Updated

Some Republicans in Congress are second-guessing a government intelligence report that Iran has abandoned its nuclear weapons program. They want a second opinion.

The National Intelligence Estimate, released last week, concludes Iran halted its weapons development program in 2003 and that the program remained frozen through at least the middle of this year. That reversed a key finding from a 2005 intelligence report, which said Iran was intently developing a nuclear bomb. An unclassified summary of the new report was released specifically to correct that impression.

The new report was received skeptically by some Republicans in Congress who believe Iran's nuclear program remains an immediate threat, and think the 2005 report is closer to the truth.

Republican Sen. John Ensign plans to introduce legislation to create a bipartisan commission to produce an alternative report on the same intelligence.

"We just see politics injected into this," said Tory Mazzola, Ensign's spokesman. "When it comes to national security we really need to remove politics. We're saying, let's take a second look."

The proposed commission is based on similar review panels convened in the mid-1970s to reconsider the intelligence agencies' analysis of the Soviet Union, and an effort in the mid-1990s to reassess the threat of ballistic missiles to the United States.

Last week, Rep. Todd Tiahrt, a Republican, said at a committee hearing he does not trust the new findings.

"I'm not sure we have a good, clear signal of what's really happening inside Iran," he said. "We've got a very big batch of mixed signals."

Twice in the last week, senior U.S. intelligence officials have been forced to defend what they consider the most rigorously reviewed National Intelligence Estimate they have produced.

Principal Deputy Director of Intelligence Donald Kerr issued a statement responding to "those questioning the analytic work and integrity" of the intelligence agencies. "We feel confident in our analytic tradecraft and resulting analysis in this estimate," he said.

And on Wednesday, a senior intelligence official told reporters that intelligence analysts are aware of the political tumult surrounding the report but do not worry about the political repercussions of their judgments. The official spoke on condition of anonymity because he was expanding on the official rebuttal.

Analysts focus on making certain their reports are sound, logical and based on reliable information, he said.

He contrasted the Iran National Intelligence Estimate with the flawed 2002 assessment of Iraq's weapons of mass destruction program. That report was produced at the request of the Senate Intelligence Committee in just a month.

The Iran report was delayed by the intelligence agencies by more than a year and a half in order to review new intelligence and to take extra care to verify sources and consider alternative explanations for what analysts were seeing, he said.

National Intelligence Estimates are the consensus judgments of the nation's 16 intelligence agencies on key concerns. Between 15 and 20 are produced every year, and they go through multiple steps to check the validity of information and analysis.

In late 2002, then-CIA director George Tenet added another safety measure after the faulty Iraq report, which turned out to rely heavily on a single, questionable source. Tenet required those who collect intelligence to sit at the table with those who analyze it to explain who their sources were, the confidence they have in them, and whether their information can be corroborated.

"There is so much more synergy now between the collection agencies and the analytic side," the senior official said. "Everyone around the table is working with the same amount of information."

The estimates are also reviewed by outside experts who are given a one-day security clearance. Some are chosen specifically because they are known to have divergent views on what the key judgments say.

"We want to understand if we are victims of group-think in this analysis," he said.