Updated

Conflicts in Iraq and Afghanistan have strained U.S. military manpower and resources and could cause delays in winning new conflicts, the nation's top military officer told Congress in a classified report.

But Gen. Richard Myers (search), chairman of the Joint Chiefs of Staff (search), told reporters at the Pentagon on Tuesday that no matter what threat occurs, the United States is prepared to take down any enemies.

"What we said is we'll be successful, we will prevail. The timelines may have to be extended, we may have to use additional resources, but it doesn't matter because we're going to be successful in the end," the general said.

The classified military risk assessment was sent to Congress on Tuesday. A senior defense official described its contents to The Associated Press by saying that the U.S. military is in a period of increased risk, but the risk should abate in a year or so.

That is the amount of time that some generals and several independent analysts suggest troops will be required to remain in Iraq.

"I think we should have troops there for at least another year. I know there is going to be demands to pull out faster than that but it seems to me that not only do we have to win the terroist war there, and I think we are winning it, but we have also got to make sure that when we leave, the Iraqis are going to be able to take care of themselves. I think that is going to take a little more time," former Secretary of State Lawrence Eagleburger told FOX News.

About 138,000 American troops are in Iraq, according to U.S. Central Command (search). Another 18,000 are in Afghanistan.

Myers said that even with troops wrapped up in Iraq and Afghanistan, the report says the trend is toward lower risk "because of the support we're getting from Congress, bigger budget supplementals to make up for some of the issues that have come out of being at war for three and a half years."

White House spokesman Trent Duffy told reporters on Tuesday that President Bush and military leaders maintain confidence that they can meet any threat "decisively" because of the additional budget and benefits being given to the military.

"President Bush has pushed for a 41 percent increase in military spending since being sworn into office," Duffy said. "We've increased spending on training, housing, quality-of-life initiatives as well as technology. And I would mention the missile defense capability as something President Bush is pushing for right at this very minute, to make sure that we have all the capabilities that we need to protect the American people."

The most notable threats aimed at the United States right now come from North Korea and Iran, two of the three members described by Bush in 2002 as creating an "axis of evil." On Sunday, North Korea lobbed a non-nuclear missile into the Sea of Japan. Pyongyang is also belived to have as many as six nuclear weapons, but is still figuring out how to get them on a missile.

Attending a Nuclear Nonproliferation Treaty conference at the United Nations on Tuesday, Iranian Foreign Minister Kamal Kharrazi said Tehran is "determined to pursue all legal areas of nuclear technology, including enrichment, exclusively for peaceful purposes."

A State Department spokesman called Iran's uranium enrichment program a covert 18-year subversion of the nonproliferation treaty.

"We continue to think that the burden is on Iran to satisfy the world that it's not going to develop nuclear weapons. There is no reason for them to have an enrichment and reprocessing program. We know how it's been used in the past. And the only way to really satisfy it and reassure the world that they're not going to be a nuclear threat is to eliminate those programs," said spokesman Richard Boucher.

With the two nations believed to be producing nuclear weapons, Homeland Security officials said on Tuesday that the U.S. government has not adequately prepared emergency personnel and the public in case of a nuclear attack on U.S. soil.

Officials told FOX News that part of the reason for that is that more first responders in the United States have been trained to deal with suicide attacks, truck bombs, chemical and biological agents rather than on a nuclear strike because a strike is much less likely than the others.

On Monday, Secretary of State Condoleezza Rice said even if North Korea should build a bomb, "the U.S. maintains significant — I want to underline significant — deterrent capability of all kinds in the Asia Pacific region."

Asked on Tuesday what would happen if North Korea invades its southern neighbor, Myers said "we would be successful," apparently referring to any U.S. effort to come to South Korea's defense.

The Pentagon prepares potential timelines for defeating potential adversaries given the soldiers, tanks, aircraft and warships to do the job. Changes to those timelines could be affected not only by threats from rogue nations but by repositioning of troops abroad in accordance with the new force structure forseen by military officials.

Eagleburger said the United States never will need to question its success in a war, but "the amount of requirement in terms of the national economy, how many people we have to have, would we have to reinstitute the draft and things like that, all are going to depend on the character of the threat and how serious it is. And we could be slow in reacting given the demands on our military, already but in the end we'll win."

FOX News' Mike Emanuel, Nick Simeone, Catherine Herridge and Sharon Kehnemui Liss contributed to this report.