Challenged by congressional leaders over its new war footing, the Bush administration has begun to emphasize that American jobs could be at risk if Saddam Hussein is allowed to maintain his grip on Kuwait.

Iraq Wednesday stepped up its accusations that the United States is preparing to attack. It denounced a plan by U.S. Marines to hold amphibious assault exercises in Saudi Arabia, calling it a "clear act of provocation."Meanwhile, President Bush told Congress Wednesday he was extending for an additional 90 days the 90-day call-up for reservists already serving in the Persian Gulf region, and the United States pressed Japan to toughen its stance in the gulf crisis.

In a setback for Arab diplomatic efforts, Saudi Arabia suggested it would probably not take part in a proposed Arab summit until Iraq pledged to pull out of Kuwait.

The Saudi foreign minister, Prince Saud al-Faisal, said any Arab meetings "will bear no fruit" unless Iraq promises to adhere to the resolutions of the emergency Arab summit held in August and of the United Nations.

King Hassan II of Morocco has proposed an emergency Arab summit to work out an Arab solution to the Persian Gulf crisis and avert war over Iraq's refusal to quit Kuwait, which it seized Aug. 2.

Saddam would consider attending the summit if he was consulted on the time and place and if the Palestinian issue is on the agenda.

Bush was meeting at the White House Wednesday with a select group of lawmakers to try to bolster support for his gulf policy. Secretary of State James A. Baker III set the stage with comments a day earlier linking the economy and the crisis.

"The economic lifeline of the industrial world runs from the gulf, and we cannot permit a dictator such as this to sit astride that economic lifeline," he said. "To bring it down to the level of the average American citizen, let me say that means jobs."

Baker suggested that a worldwide economic recession could result if Saddam is not checked and the security of gulf oil reserves ensured.

The call for greater Japanese support for the anti-Iraq coalition came from Vice President Dan Quayle, who met in Tokyo with Japanese Prime Minister Toshiki Kaifu. Quayle said he told Kaifu Washington would like a Japanese presence in the gulf in addition to the billions of dollars Tokyo has committed there.

Kaifu had proposed sending Japanese soldiers to the gulf for non-combat duty, but the measure failed to win enough support in Parliament. The government and the opposition have now agreed to draft a new measure calling for the dispatch of Japanese civilians as part of peacekeeping efforts.

Still, more allied soldiers and hardware may be on their way to join the U.S. expeditionary force that has gathered in the Saudi desert as the chief challenger to Saddam.

The Times of London reported Wednesday that Britain is expected to send an additional 6,000 troops and more than 100 additional tanks to the gulf, increasing its ground forces there to 15,500 and its tanks to more than 220.

The Bush administration has indicated that its readiness to attack Iraqi forces to dislodge them from Kuwait, if saber-rattling and a U.N.-ordered embargo on trade with Iraq fail.

On Tuesday, key Democratic and Republican senators asked Bush to convene an emergency session of Congress to discuss the administration's gulf policy.

The White House quickly called such a session unnecessary. Said press secretary Marlin Fitzwater: "There is no war."

Iraq's harsh criticism of the U.S. plan for an amphibious assault exercise in Saudi Arabia came a day after the Pentagon announced it. Pentagon spokesman Pete Williams would not say when or exactly where the exercise would be held.

The Washington Times said it would be held 10 miles from Kuwait.

"This behavior constitutes a clear act of provocation that exposes, along with other evidence, America's aggressive intentions against Iraq," the official Iraqi News Agency quoted an unidentified Iraqi government source as saying.