UNITED NATIONS - The leaders of U.N. weapons inspections teams, responding to intense pressure from the United States and Britain, said yesterday that they would delay their return to Iraq until the Security Council gives them new instructions to guide their work.

In Washington, President Bush's request for authority to use force against Iraq advanced on Capitol Hill, with a House panel voting its approval and Senate leaders predicting wide margins of bipartisan support.

In a closed meeting with the weapons experts, the 15 nations that sit on the council moved significantly toward agreement that they should toughen the rules governing the inspections, diplomats said.

But even as Bush warned again, in strong terms, that he would take military action to disarm Iraq if the United Nations did not, the council came no closer to accord on a strong resolution including an authorization of military force.

"The choice is up to the United Nations to show its resolve," Bush told Hispanic leaders in the Eisenhower Executive Office Building in Washington. "The choice is up to Saddam Hussein to fulfill his word. And if neither of them acts, the United States, in deliberate fashion, will lead a coalition to take away the world's worst weapons from one of the world's worst leaders."

The Bush administration, with its full-court press in Washington and world capitals, appeared to have made headway toward persuading the skeptical council to adopt a new measure requiring Iraq to accept far more intrusive inspections that would include the palaces of the Iraqi leader.

But France and Russia, two veto-bearing council members, dug in their heels against giving the United States and its ally Britain blanket permission in an initial resolution to launch a strike to topple Hussein.

The council heard from Hans Blix, head of the biological and chemical weapons inspection team based here, and Mohamed El-Baradei, director of the International Atomic Energy Agency, on their meetings in Vienna, Austria, this week with Iraqi officials.

"It would be awkward if we were doing inspections and then a new mandate with changed directives were to arise," Blix said after the council session. Asked whether he is planning to delay the weapons teams' departure for Baghdad, he said, "If the council puts some new suggestions or directives to us, of course we are in their hands."

Blix reported to the council that there were "loose ends" left over from his talks with the Iraqi officials. The issue of immediate access for the inspectors to Hussein's compounds was not resolved, Blix and Baradei reported.

Blix said he would welcome a new resolution to guide his work. Many of his "loose ends" are addressed in a draft resolution the United States and Britain have drawn up but not yet introduced in the council.

In the meeting, France and Russia said they were ready to clarify the mandate for the inspectors, diplomats said.

"We believe that a sufficient legal base already exists for the resumption of the U.N. inspections," Russian Deputy Foreign Minister Alexander Saltanov said, according to the Interfax news agency.

While the tide seemed to shift in favor of a French proposal for two resolutions - one to set up the inspections and another to authorize military action if they fail - American officials insisted forcefully on their single draft resolution.

It calls for "all necessary means" against Iraq if Baghdad makes any move to block the arms inspectors. The resolution has to include "a mechanism to deal with noncompliance," an administration official said. "It's not negotiable."

Secretary of State Colin L. Powell kept up intensive telephone diplomacy yesterday, speaking with the British foreign secretary, Jack Straw; the French foreign minister, Dominique de Villepin; and his Russian counterpart, Igor S. Ivanov. "I am optimistic that we will find a way forward in the Security Council," Powell said.

Today, Powell and the national security adviser, Condoleezza Rice, are to meet in Washington with Blix to "talk about his capabilities and ask if he needs anything more from us," a senior Bush administration official said.

In Congress, Senate Minority Leader Trent Lott, a Mississippi Republican, predicted that Bush would get the authority he wants by next week.

Reflecting the Senate's determination to move ahead, the chamber voted 95-1 on a procedural motion that clears the way for votes next week. The lone dissenter was Sen. Robert C. Byrd, a West Virginia Democrat.

The House International Relations Committee turned back efforts to weaken the resolution embraced by Bush and House leaders and approved it 31-11, sending it to the full House for debate next week. Illinois Republican Rep. Henry J. Hyde, the chairman, asked members "to support not the president but the cause that is embodied in this resolution."

Senate Majority Leader Tom Daschle announced that separate votes would be held next week on two alternatives that would put more limits on presidential authority.

Meanwhile, members of the Senate Intelligence Committee said yesterday that the CIA has been withholding information it requested on U.S. military action in Iraq.

Also yesterday, allied forces dropped thousands of leaflets over southern Iraq, warning Iraqi forces against firing at British and U.S. planes that patrol the no-fly zone. Iraqi forces responded by firing on a plane delivering the leaflets. That led allied forces to bomb an air defense operations center, U.S. Central Command officials said.