WASHINGTON — A new report on Iraq's illicit weapons program is expected to conclude that Saddam Hussein's government had a clear intent to produce nuclear, chemical and biological weapons if U.N. sanctions were lifted, government officials said Thursday. But the report finds no evidence that Iraq had begun any large-scale program for weapons production by the time of the U.S. invasion last year, the officials said.

The most specific evidence of an illicit weapons program, the officials said, has been uncovered in clandestine labs operated by the Iraqi Intelligence Service, which could have produced small quantities of lethal chemical and biological agents, though probably for use in assassinations, not to inflict mass casualties.

A draft report of nearly 1,500 pages that is now circulating within the government essentially reaffirms the findings of an interim review completed 11 months ago, the officials said. But they said it adds considerable detail, particularly on the question of Iraq's intention to produce weapons if U.N. sanctions were weakened or lifted, a judgment they said was based on documents signed by senior leaders and the debriefings of former Iraqi scientists and top officials, as well as other records.

The officials said the report would portray a more complicated and detailed picture, based on a far more extensive examination of suspected Iraqi weapons sites and records, as well as the debriefings. They said new information in the draft report based on on-site inspections of clandestine labs described the possibility that they were intended to provide small quantities of poisons.

A final version of the report, by Charles A. Duelfer, the top American weapons inspector in Iraq, is expected to be made public within the next several weeks.

In its current form, the report reaffirms previous interim findings that there is no evidence that Iraq possessed stockpiles of illicit weapons at the time of the American invasion in March 2003, the officials said. Prewar intelligence estimates that said Iraq actually possessed chemical and biological arsenals and was reconstituting its nuclear weapons program were cited by the Bush administration as the major rationale for war.

With the presidential election campaign in its final weeks, Republicans and Democrats are likely to seize on separate aspects of the report in an effort to score political points.