Nearly all of the Security Council's 15 members have said they want to see, in the Russian ambassador's words, "undeniable evidence" from the United States that Iraq retains weapons of mass destruction before considering an attack on Iraq.

"America is saying, 'Just trust us,' " a council diplomat said. "But the only thing we can know for sure is that they are ready to invade Iraq no matter what."

Powell was expected to argue that Iraqi President Saddam Hussein is violating a United Nations resolution by working to hide illegal weapons from U.N. inspectors, aides said. He is expected to cite telephone intercepts and surveillance photographs in urging the council to support the possible use of force if Saddam refuses to disclose his weapons stockpiles.

Even if Powell, who was to be accompanied by CIA agents, presents convincing evidence, several key council members — France, Russia, China, Germany and Mexico — have signaled that they won't be swayed from their belief that the best way to disarm Iraq is through inspections, not force.

"We are going to listen very carefully to Mr. Powell," Mexican Ambassador Adolfo Aguilar Zinser said yesterday, "and we have an open mind about what he's going to say. But we feel very strongly about the continuation of inspections.

"Whatever evidence is presented should be useful to the work of the inspectors and allow them to disarm Iraq through peaceful means."

His comments echoed French President Jacques Chirac's statement after meeting British Prime Minister Tony Blair yesterday. Chirac said that France is opposed to military action while the inspectors' work is unfinished. Any action, Chirac added, should be taken only with the full Security Council's blessing.

The lack of trust in the United States irks those who see today's presentation as the culmination of months of careful case-building against Iraq.

"I must say I sort of find it astonishing that the issue is whether you can trust the U.S. government," Deputy Defense Secretary Paul Wolfowitz said in a recent speech. "The real issue is, can you trust Saddam Hussein?"

At the risk of revealing the extent of U.S. intelligence capabilities, Powell will try to demonstrate exactly how Iraqis are actively concealing weapons and deceiving inspectors, including interceptions of phone calls ordering sites to be cleaned up before the U.N. teams arrive.

And Powell is expected to scold inspectors, noting that they have only acted on about 5 percent of "strong" intelligence tips that the United States and others have provided. CIA director George Tenet and his deputy, John McLaughlin, will attend Powell's briefings to underline their importance and the quality of the intelligence, U.S. officials said.

The next step will be for the United States and Britain to convince skeptics that given Iraq's track record, more time won't make a difference for inspectors and they should approve the "serious consequences" of military action that they signed on for in last fall's resolution.

A second resolution authorizing force is "preferable, but not necessary," President Bush has said. The White House is betting that when it comes time to vote, Germany and Syria will opt out but that France and others won't want to be left behind.