Updated

The intelligence community has high confidence that Iran had a covert nuclear weapons program that it never acknowledged and continues to deny, National Security Adviser Stephen Hadley said Monday, but the program is currently halted although perhaps not indefinitely.

The assessment, outlined in the latest National Intelligence Estimate, states that Iran stopped its nuclear weapons development program in the fall of 2003 under international pressure, but is continuing to enrich uranium and could be capable of developing a weapon as early as late 2009.

The findings are a change from two years ago, when U.S. intelligence agencies believed Iran was determined to develop a nuclear capability and was continuing its weapons development program.

Click here to read the unclassified NIE (pdf).

Hadley said the change in assessment does not suggest a failure on the part of the U.S. intelligence community, but a success in finding the true status of the program.

Hadley said no secret has been more closely kept than Iran's nuclear weapons pursuits.

"They are very good at his business of keeping secrets," he told reporters in an afternoon press conference at the White House.

Prior to Hadley's on-the-record, for-attribution briefing, four of the nation's top intelligence officials said they believe it remains Iran's "latent goal" to develop a nuclear weapon, but that "gaps remain" in their ability to collect and analyze information on what they called "probably the hardest intelligence target there is."

The intelligence community considers the Iranian regime a "rational actor" and a "unitary actor," meaning internal differences of opinion amongst various factions inside the regime are not contributing to a schism in the regime's actions or calculus.

Hadley said the latest NIE, briefed to President Bush last week and given to the congressional intelligence committees on Monday morning, suggests the U.S. has taken the right approach to dealing with the Islamic republic. He described the strategy as one of "intensified international pressure along with the willingness to negotiate a solution that serves Iranian interests while insuring the world it will never have to face a nuclear-armed Iran."

"On balance, the estimate is good news," Hadley said. "On one hand it confirms that we were right to be worried about Iran seeking to develop nuclear weapons. On the other hand, it tells us that we have made some progress in trying to insure that that does not happen. But it also tells us that the risk of Iran acquiring a nuclear weapon remains a very serious problem."

The unclassified portion of the NIE being made public is nine pages in length, five of which explain methodology. The key judgments conclude with "high confidence" that:

— Until fall 2003, Iranian military entities were working under government direction to develop nuclear weapons;

— In fall 2003, Tehran halted its nuclear weapons program;

— The halt lasted at least several years;

— Iran has the scientific, technical and industrial capacity eventually to produce nuclear weapons if it decides to reverse course;

— The halt, and Tehran's announcement that it has suspended its declared uranium enrichment program and signed additional safeguards relating to the Nuclear Non-Proliferation Treaty are "primarily in response to increasing international scrutiny and pressure resulting from exposure of Iran's previously undeclared nuclear work"; and

— Iran will not be technically capable of producing and reprocessing enough plutonium for a weapon before about 2015.

The judgments find with "moderate-to-high confidence" that:

— Iran does not currently have a nuclear weapon;

— Tehran at a minimum is keeping open the option to develop nuclear weapons; and

— Iran has not obtained enough weapons-usable fissile material to develop a nuclear weapons, though the NIE assesses with low confidence the importation at all of some material. The report does not rule out that Iran "has acquired from abroad — or will acquire in the future — a nuclear weapon or enough fissile material for a weapon."

The judgments also find with "moderate confidence" that:

— Tehran had not restarted its nuclear weapons program as of mid-2007, but the NIE notes that its intentions to develop weapons is unknown;

— The earliest possible date Iran would be technically capable of producing enough highly enriched uranium for a weapon is late 2009, but that this is very unlikely;

— More likely is that it would be technically capable of producing enough highly enriched uranium for a weapon sometime between 2010 and 2015;

— Iran probably would use covert facilities rather than its declared nuclear sites in its effort to produce highly enriched uranium for a weapon.

The report concludes that Iran resumed its declared centrifuge enrichment activities in January 2006 despite the continued halt in the nuclear weapons program, and made significant progress in 2007 installing centrifuges at Natanz, its chief nuclear plant.

In those efforts, Iranian agencies are still working on creating the technology that could be used for producing nuclear weapons, if it turned toward that activity.

"Since fall 2003, Iran has been conducting research and development projects with commercial and conventional military applications — some of which would also be of limited use for nuclear weapons," the report states.

What Does the Report Mean for the U.S.?

The report is the outcome of a request made earlier this year by Congress calling for a new intelligence estimate on Iran. Hadley said production of the report was delayed in part to process new intelligence that was received in the last few months and conclusions about it were reached last Tuesday.

Senate Majority Leader Harry Reid said Monday he asked for the new NIE because he was concerned that Bush was beating the drum for war with Iran.

"Early reports of the NIE judges that Iran halted its nuclear weapons program four years ago ... We should be having a surge of diplomacy with Iran. And based upon this, I think it would be a pretty good idea," Reid said.

"I strongly urge President Bush to pursue a clear-eyed, serious diplomatic effort, with both carrots and sticks, to prevent Iran from restarting its nuclear weapons program. We must not lose sight of this threat," said House Intelligence Committee Chairman Silvestre Reyes, D-Texas.

Stopping Iran from acquiring a nuclear weapon must be one of the highest priorities of the United States and the international community. Iran is the world's preeminent state sponsor of terrorism, and there are indications that the Al Quds force of Iran's Revolutionary Guard Corps has assisted insurgents in lethal activity against U.S. forces in Iraq," Reyes said.

2008 presidential candidates were also quick to draw conclusions about U.S. policy based on the report.

"The new National Intelligence Estimate shows that George Bush and Dick Cheney's rush to war with Iran is, in fact, a rush to war," said Democratic candidate John Edwards. "The new NIE finds that Iran halted its nuclear weapons program in 2003 and that Iran can be dissuaded from pursuing a nuclear weapon through diplomacy. This is exactly the reason that we must avoid radical steps like the Kyl-Lieberman bill declaring Iran's Revolutionary Guard a terrorist organization, which needlessly took us closer to war. And its why I have proposed that we pursue a comprehensive diplomatic approach instead."

"For years now, the Islamic Republic of Iran has defied and played games with every international effort aimed at persuading the country to halt enriching uranium. Sanctions and other pressures must be continued and stepped up until Iran complies by halting enrichment activities in a verifiable way," said Republican candidate Rudy Giuliani.

Despite the new conclusions, the report makes clear that intelligence gaps mean a judgment can't be made on whether Tehran is willing to continue the halt of its nuclear weapons program indefinitely or has set specific deadlines or criteria to prompt the continuation of the program.

It also concludes that Iran's decision to halt the program is likely based on a cost-benefit approach, influenced by international pressure, "rather than a rush to a weapon irrespective of the political, economic, and military costs."

"In our judgment, only an Iranian political decision to abandon a nuclear weapons objective would plausibly keep Iran from eventually producing nuclear weapons — and such a decision is inherently reversible," the report states.

"If we are to avoid the grim choice of accepting an Iran on the path to nuclear weapons or considering the use of force, we need to intensify our pressure on Iran while making clear that if they do suspend enrichment, there is an opportunity for better relations with the international community," Hadley said.

In the earlier briefing, the intelligence officials took pains to explain why the last NIE, dated May 2005, failed to detect the central new conclusion of the present one: namely that Iran halted its covert nuclear weapons program in late 2003 (actual programs for weaponization were what was halted; other activities that could contribute to a nuclear weapon, such as uranium enrichment and research into delivery systems, remain ongoing).

"We had a paucity of data," one official stated, adding such shortcomings are "just part of the business." The officials said the Iranians "deliberately, carefully, and ... effectively" kept their nuclear weapon program hidden, and, too, the secret halt to it.

The officials said they are more inclined now than they were in 2005 to believe the Iranians are rational actors, because the regime's susceptibility to international pressure — a key factor in the halting of the nuclear weapons program — suggests the Iranians' "cost-benefit" model is surprisingly similar to the kind the U.S. would employ.

Asked if the intelligence community's state of knowledge about current Iranian nuclear activities is "diminishing," as the International Atomic Energy Agency recently said of itself, the officials suggested the opposite: that drawing on all available sources, including signals intelligence, open-source, the IAEA and other resources, the American intelligence community has new information and better insight into old information than it did in 2005.

However, the officials agreed the IAEA's knowledge about current Iranian activity is diminishing. One official stated flatly that the Iranians have concealed nuclear activities from the IAEA. One source of information available to analysts this time around were the TV images of the exterior and interior of Iran's pilot fuel enrichment facility at Natanz, which gave intelligence professionals "data" that "helped us understand what they have."

The officials said counterintelligence analysts were asked at one point to assess whether the halt in Iran's weaponization program was initiated as a "strategic deception," namely, a ruse. "We gamed more than half a dozen such scenarios," one official stated. But the analysts reached the conclusion such a scenario was "plausible but not likely."

Although the officials as a rule, respecting the norms of their craft, declined to offer policy prescriptions based on their findings, the most senior official present did cite the finding that the Iranians are susceptible to international pressure and say that such pressure should "continue" as a way to "allow IAEA to have significant visibility into the program."

The NIE does not address what conditions would need to obtain in order for the Iranian leadership to take the decision to restart the weaponization program. At one point one official stated: "I don't expect them to admit (to having maintained or halted a longstanding covert nuclear weapons program). I assume they'll just say we're wrong."

Asked if the war in Iraq was among the factors that likely contributed to the halt of the weaponization program in late 2003, the officials suggested it was part of an "atmosphere" that also included at that time the "implosion" of the A.Q. Khan network; the decision by Libya to abandon its weapons of mass destruction programs and cooperate with American authorities probing its origins; and the threat of U.N. sanctions.

The impact of international pressure is beyond dispute, the officials said, a "cause-and-effect" relationship backed up by an "evidentiary trail."

The officials also went to great lengths to emphasize how differences of opinion amongst the intelligence agencies were spotlighted and not brushed over in the final product. They said they were "exceptionally careful" in preparing this report because of the "lessons learned" from the mistakes made regarding Iraq's weapons of mass destruction program.

FOX News' James Rosen and Sharon Kehnemui Liss contributed to this report.