Recent statements by senior U.S. officials that Iraq may be close to developing a nuclear weapon are based on a new intelligence estimate that the Middle East crisis could eventually compel Iraqi President Saddam Hussein to make a primitive nuclear device using a stockpile of highly enriched uranium in the hands of his government, knowledgeable U.S. officials disclosed yesterday.

The officials said the United States has no evidence that any of the uranium, subject to international inspection so far, has been diverted or will soon be diverted. They said they did not dispute a statement this week by the International Atomic Energy Agency (IAEA) in Vienna that its inspectors found the fissile uranium intact during a routine inspection last week.

Experts agree that the enriched uranium, which exists in fuel assemblies from one of Iraq's nuclear reactors, must be processed before it can be used in a nuclear weapon and that such an effort would almost surely be detected.

The officials also said the U.S. intelligence community has not altered its previous estimate that Iraq probably could not develop a nuclear weapon in less than five to 10 years without diverting the enriched uranium.

They said there also was no evidence that Iraq had substantially stepped up its longstanding effort to develop an atomic weapon at sites that are not subject to IAEA inspection.

These statements, from officials who asked not to be named, appeared to conflict with public remarks by other senior Bush administration officials who have said that Iraq could develop a nuclear weapon soon at the sites not subject to outside inspection and could be closer now than Iraq was a few months ago to making a crude nuclear weapon.

White House press secretary Marlin Fitzwater, responding to criticism of the administration's public statements, took issue yesterday with the new IAEA report, saying the agency's inspectors "saw only what Iraq wants them to see." He added, "We don't believe they saw all the information."

Fitzwater's comments were in line with remarks by Deputy Secretary of State Lawrence S. Eagleburger Tuesday that "the statements {about Iraq's nuclear bomb-making potential} that have been made by the secretary of state, the secretary of defense and the president {in recent days} are based on fairly substantial evidence . . . that there is substantial un-safeguarded nuclear activity going on in Iraq."

But a U.S. official familiar with the latest intelligence report said, "There's been no new development in the sense that Iraq is any closer to acquiring a nuclear weapons capability in less than five to 10 years."

The official said that the only way this timetable might be shortened is if Saddam decided to flout international controls on his stockpile of fissile material and develop a crude weapon after six to 12 months of concentrated effort. The official said this estimate was "a worst-case" assessment, and that the "median" U.S. estimate involved a much longer period.

A "crude weapon" is one that may not be "deliverable, effective or even explodable," the official said.

Several officials said the intelligence community had not previously attached any credence to scenarios involving Saddam's potential diversion of the highly enriched uranium.

But the latest report raised this possibility for the first time because "he now has more of a motive for doing it," one official said.

"Simply put, if he's up against a wall, he may try to make a weapon quickly . . . and we wouldn't know about it until next spring," when IAEA inspectors are expected to make their next routine visit to Iraq, the official said.

The administration's recent public claims about Iraq's nuclear program were disputed yesterday by two former high-ranking military officials, and on Tuesday by a former secretary of defense, in testimony before the Senate Armed Services Committee.

Retired admiral William J. Crowe Jr., chairman of the Joint Chiefs of Staff from 1985 to 1989, dismissed as "exaggerated" statements that Iraq is poised to develop a nuclear arsenal.

Retired Air Force general David C. Jones, who served as chairman from 1978 to 1982, also described the Iraqi nuclear threat as a "long-term issue" and said, "I do not think it is a justification today to attack Iraq just for that purpose."

James R. Schlesinger, a former director of the Central Intelligence Agency and secretary of Energy and Defense, said, "We are dealing with a threat down the road."

Schlesinger suggested that the Bush administration has chosen to emphasize the immediacy of Iraq's nuclear threat to bolster support for going to war.

"I think that it is no accident," he said, "that last Tuesday the New York Times published a poll that indicated . . . the only reason that the American public supported going to war in the Middle East would be to eliminate Iraq's nuclear capability," and that since then, administration officials have made repeated statements about this threat.

"We may recall that in the days of flourishing communism in Moscow that it used to be said, 'That is no accident, comrade,' " Schlesinger said.

Expressing a view that several officials said paralleled the current U.S. intelligence assessment, Schlesinger said, "If the Iraqis were to attempt to use {the enriched uranium}, we would detect it because of the failure to meet inspection" next year. In addition, he said, "It would take them on the order of nine months to a year minimum" before Iraq could develop a large and cumbersome weapon with this material.

Several officials said any aircraft capable of delivering the weapon could readily be shot down by U.S. military forces on Saudi Arabia territory.

Staff writer Ann Devroy contributed to this report.