WASHINGTON, Oct. 28— The director of a top American spy agency said Tuesday that he believed that material from Iraq's illicit weapons program had been transported into Syria and perhaps other countries as part of an effort by the Iraqis to disperse and destroy evidence immediately before the recent war.

The official, James R. Clapper Jr., a retired lieutenant general, said satellite imagery showing a heavy flow of traffic from Iraq into Syria, just before the American invasion in March, led him to believe that illicit weapons material ''unquestionably'' had been moved out of Iraq.

''I think people below the Saddam Hussein-and-his-sons level saw what was coming and decided the best thing to do was to destroy and disperse,'' General Clapper, who leads the National Imagery and Mapping Agency, said at a breakfast with reporters.

He said he was providing a personal assessment. But he said ''the obvious conclusion one draws'' was that there ''may have been people leaving the scene, fleeing Iraq, and unquestionably, I am sure, material.'' A spokesman for General Clapper's agency, David Burpee, said he could not provide further evidence to support the general's statement.

But other American intelligence officials said General Clapper's theory was among those being pursued in Iraq by David Kay, a former United Nations weapons inspector who is leading the American effort to uncover the weapons cited by the Bush administration as the major reason for going to war against Iraq.

General Clapper's comments came as the Central Intelligence Agency prepared to defend its prewar assertions that Iraq had chemical and biological weapons and that it sought to reconstitute its nuclear program. The director of central intelligence, George J. Tenet, has written a letter to the chairman and vice chairman of the Senate Select Committee on Intelligence saying the agency will be ready to provide an assessment by late November.

In the letter, the contents of which were described by several intelligence officials on Tuesday, Mr. Tenet proposed that a team headed by John McLaughlin, the deputy director of central intelligence, provide a briefing for the committee after Nov. 20, when the agency's internal review is expected to be completed.

General Clapper's agency is responsible for interpreting satellite photographs and other imagery. He declined to answer a question about whether he believed that illicit Iraqi weapons material might have been smuggled into any other country.