New Data, New Methods, New Conclusion

The spy agencies had swallowed hard and pledged to do better after a presidential commission in March 2005 issued a blistering accounting of the intelligence failures leading to the Iraq war.

But a National Intelligence Estimate on Iran that was issued two months later said Iran’s leaders were working tirelessly to acquire a nuclear weapon — a finding that, like the prewar intelligence on Iraq, has now been acknowledged to have been wrong in one of its chief conclusions.

Current and former intelligence officials insist that much of the 2005 Iran report still holds up to scrutiny.

At the same time, they acknowledge that in retrospect, some of its conclusions appear to have been thinly sourced and were based on methods less rigorous than were ultimately required under an intelligence overhaul that did not begin in earnest until later.

It was also written by some of the same team that had produced key parts of the flawed Iraq estimate. Robert D. Walpole oversaw both reports as the national intelligence officer responsible for assessing illicit-weapons programs.

Robert Hutchings, who as head of the National Intelligence Council from 2003 to early 2005 oversaw early production of the 2005 Iran assessment, said the quality of information about Iran’s nuclear program should have made American intelligence analysts wary of judging anything with “high confidence.” That was how the 2005 report described the basis for its assertion that Iran was determined to develop nuclear weapons, a conclusion that has been disavowed.

“The fact that we’ve reversed course two years later suggests that the high confidence back then wasn’t warranted,” said Mr. Hutchings, who had left the intelligence council by the time the intelligence estimate was produced in May 2005.

Paul R. Pillar, another member of the National Intelligence Council in 2005, said it was a “fair point” to criticize intelligence agencies for overstating their confidence in the judgments of the 2005 estimate. But he said the judgment that Iran is determined to obtain the bomb could prove correct in the long run.

The intelligence agencies’ 2005 finding that Iran was pursuing a nuclear weapons program was consistent with strong warnings about Iran issued at the time by Bush administration officials, including Vice President Dick Cheney and John R. Bolton, then the under secretary of state. But there has been no indication that policy makers sought in any way to influence the agencies’ conclusions on Iran, which like all intelligence assessments are supposed to be immune from political pressure.

The officials said that the 2007 estimate was an attempt by spy agencies to examine the Iran problem in a new light, and that in the process they recast many of their principal judgments about Iran’s weapons programs that might have relied on outdated information.

Some sources used for the 2005 estimate were discarded for the new report, and some old information that intelligence agencies did not use for the 2005 estimate was re-examined and included in the estimate released Monday.

The new intelligence estimate concludes with “high confidence” that Iran halted work on its nuclear weapons program in 2003.

Senator John D. Rockefeller IV of West Virginia, the Democratic chairman of the Senate Intelligence Committee, called it “puzzling” and “disturbing” that intelligence agencies in 2005 could produce a flawed estimate so soon after what he called the Iraq “debacle.”

Government officials who have read both estimates said the 2005 report was filled with analysis based on somewhat murky knowledge of Iran’s capabilities and the goals of its leaders. They said the new intelligence estimate contained very specific information to back up unusually confident conclusions about the state of Iran’s weapons program.

Government officials said the new judgments were grounded largely in information from human sources that is buttressed by other information gathered by spy satellites and communications intercepts.

John E. McLaughlin, the deputy director of the Central Intelligence Agency from 2000 to 2004 and the acting director for two months in 2004, said the agencies’ shifting view between 2005 and 2007 simply showed how difficult intelligence was to get right.

“In 2005, what we had was what we had,” Mr. McLaughlin said. “I think people should take comfort from the fact that they’ve changed their view.”

Over the past year, officials have put into place rigorous new procedures for analyzing conclusions about difficult intelligence targets like Iran, North Korea, global terrorism and China.

Analysts from disparate spy agencies are no longer pushed to achieve unanimity in their conclusions, a process criticized in the past for leading to “groupthink.” Alternate judgments are now encouraged.

In the case of the 2007 Iran report, “red teams” were established to test and find weaknesses in the report’s conclusions. Counterintelligence officials at the C.I.A. also did an extensive analysis to determine whether the new information might have been planted by Tehran to throw the United States off the trail of Iran’s nuclear program.

One result was an intelligence report that some of the intelligence community’s consistent critics have embraced.

“Just possibly, the intelligence community may have taken a major step forward,” Senator Rockefeller said.