WASHINGTON (AP) - The Bush administration pressed Congress to take the lead in authorizing force against Iraq yesterday after the U.S. campaign for a tough new U.N. resolution was undercut by Saddam Hussein's offer on inspections. As the White House talked tough, United Nations weapons inspectors began planning their return to Baghdad.

"It serves no U.S. or U.N. purpose to give Saddam Hussein excuses for further delay," Defense Secretary Donald Rumsfeld asserted.

Iraq's announcement that it would accept the return of international weapons inspectors nearly four years after they left divided the Security Council. The United States and Britain pursued a resolution to force Iraq to disarm. But Russia and France were opposed, as were Arab nations.

Rumsfeld, in testimony to the House Armed Services Committee, and President Bush, in a White House meeting with top congressional leaders, dismissed the Iraqi leader's 11th-hour overture as a stalling tactic.

"He's not going to fool anybody," Bush said.

Rumsfeld suggested that Iraq had concealed evidence of its weapons programs in a labyrinth of tunnels and other elaborate hiding places, certain to complicate and prolong any new inspection effort.

While United Nations officials in New York prepared for the inspectors return, the United States and Britain began working on a new resolution aimed at authorizing use of force should Baghdad fail to comply with U.N. Security Council resolutions.

Western diplomats said the U.S.-British draft would likely include new instructions for weapons inspectors and a timetable for disarmament that would be tighter than one laid out in an existing resolution passed in December 1999.

U.S. officials said they did not intend to let Iraq's maneuver blunt their efforts for such a resolution. "I see nothing to suggest that the timing has changed for what the United Nations Security Council is considering," said Bush press secretary Ari Fleischer.

Still, Iraq's invitation to give international inspectors unfettered access to suspected weapons sites after a four-year absence divided the Security Council and prompted the White House to step up its pressure on both allies and Congress.

"Only certainty of U.S. and U.N. purposefulness can have even the prospect of affecting the Iraqi regime," Rumsfeld said.

"It is important that Congress send that message as soon as possible - before the U.N. Security Council votes."

Rumsfeld testified as the White House put the finishing touches on its proposed congressional resolution.

The White House plans to give it to lawmakers as early as today. It would give Bush maximum flexibility to confront the threat posed by Saddam's weapons of mass destruction, and includes much of the language found the 1998 law calling for a regime change in Iraq, a senior White House official said.

Outlining the administration's case, Rumsfeld told the House panel: "No terrorist state poses a greater and more immediate threat to the security of our people and the stability of the world than the regime of Saddam Hussein in Iraq."