The chief U.N. nuclear inspector said Sunday that world powers now opposed to using force against Iraq could change their minds if Baghdad doesn't show more willingness to reveal evidence of weapons programs.

Mohamed ElBaradei, who heads the U.N. search for banned weapons along with Hans Blix, told The Associated Press that the onus was on Iraq, not the U.N. inspectors searching for weapons of mass destruction, to prove that it had nothing to hide.

Secretary of State Colin Powell's call for support for military action was rebuffed Friday in a stormy U.N. Security Council meeting. Most Council members lined up behind the foreign ministers of France, Russia and Germany, who called for more inspections after Blix and ElBaradei reported some progress.

ElBaradei, who heads the Vienna-based International Atomic Energy Agency, said council sentiment could swing toward Washington unless Baghdad convincingly demonstrates its eagerness to reveal all evidence of past and present nuclear, chemical and biological weapons programs.

"It is clear that the Security Council would like to give the inspections more time," ElBaradei said flying to Vienna from New York. "Having said that, Iraq should not get the wrong message."

"The Security Council is still very impatient, the Security Council believes that Iraq still is not cooperating the way it should cooperate," he said.

Despite majority Security Council sentiment that inspections should continue for now, "everybody is of the view that force might not be excluded as a last resort, and everybody is also saying that Iraq has a limited time to comply," ElBaradei said.

Rattled by the outpouring of anti-war sentiment, the United States and Britain began reworking a draft resolution Saturday to authorize force against Saddam Hussein. But diplomats, speaking on condition of anonymity, said the final product may be a softer text that does not explicitly call for war, unlike the draft originally planned.

Nearly four years ago, inspectors sent to Iraq in the aftermath of the 1991 Gulf War withdrew on the eve of U.S.-British airstrikes amid allegations that Baghdad was not cooperating with the teams. They returned in November under a U.N. resolution committing Iraq to cooperate and implying, but not explicitly stating, the threat of military action if it does not.

ElBaradei and Blix said Iraq's decision to allow surveillance flights, provide new documents and investigate past arms stockpiles showed improved cooperation.

On Sunday, ElBaradei said he expected high-altitude U-2 surveillance flights to begin "within the next few days," boosting the expanding search for banned weapons. But he stressed that the burden of proof was on Iraq to do more to show it was not hiding anything.

Specifically, he urged more scientists and military experts to consent to being interviewed without the presence of government minders, and in some cases outside the country. Up to now, only three Iraqis have consented to interviews alone or without taping their comments.

ElBaradei has previously suggested he would need several more months for his nuclear inspection teams. Picking up on a French suggestion to expand the number of inspectors, now reported to be at around 90, he said Sunday that he and Blix would "like to continue to build capacity."

More inspectors would allow for multiple teams to conduct simultaneous inspections and have U.N. customs experts check shipping documents for evidence of smuggling related to weapons of mass destruction.

He said his inspectors were "making progress even without 100 percent Iraqi cooperation," but suggested crews searching for biological and chemical weapons were more dependent on help from the Iraqis.

Whereas nuclear weapons programs "leave fingerprints" -- radioactive traces -- chemical and biological agents can easily be hidden, he said.

"They have to come with whatever they have," he said of the Iraqis. "They still have to come with the evidence to exonerate themselves and they should do that in the next few weeks, because we're still talking of a limited time span."