ASHINGTON, Sept. 14 ・Moving swiftly in America's new war on terrorists, a senior State Department official today met with 15 Arab representatives and gave them a stark choice: either declare their nations members of an international coalition against terrorism, or risk being isolated in a growing global conflict.

Unusually, the meeting included the ambassador of Syria, a country long on the State Department's list of those that foster terrorism. It followed a 98-to-0 vote in the Senate to give President Bush the power to use "all necessary and appropriate force" to respond to the terror attacks on the United States this week.

The House approved the use of force resolution late today by a vote of 420-1.

President Bush said after the House voted: "I am gratified that the Congress has united so powerfully by taking this action. It sends a clear message ・our people are together and we will prevail."

The lone member of Congress to vote against the measure, Rep. Barbara J. Lee, Democrat of California, said the nation risked entering an open-ended war without a clear target. She said in a statement, "I am convinced that military action will not prevent further acts of international terrorism against the United States."

Mr. Bush took the first concrete step toward a military response to Tuesday's acts of terror, giving the Pentagon authority to activate as many as 50,000 reserve troops to maintain aerial patrols over American cities and to strengthen security at crucial military and civilian installations. Some of the reservists could also be deployed overseas to provide security at American bases or perform other support missions, Pentagon officials said.

As Congress was also voting today to authorize $40 billion for increased military preparedness and disaster relief, William J. Burns, assistant secretary of state for Near East affairs, met with the Arab envoys and delivered what a senior administration official called a simple message: "The time has come to choose sides."

The State Department described the nascent antiterror coalition as embracing "all civilizations," not just the West. Secretary of State Colin L. Powell said at a news conference today, "This has become a new benchmark, a new way of measuring the relationship and what we can do together."

Mr. Burns read to the Arab envoys ・who included a representative of the Palestinians, whose leader, Yasir Arafat, has yet to meet with the president ・a list of actions their nations were expected to take against terrorism, including the arrest and prosecution of terrorists on a country's soil.

In addition, the State Department sent a cable to all its embassies and posts around the world today listing the conditions that nations were expected to meet in order to qualify for membership in the antiterror coalition.

Quoting from the cable, a State Department official said it included a demand that each country must "wrap up and prosecute terrorists on your own soil."

The Arab representatives were not given a deadline for deciding whether to sign on to the antiterror cause. Nor was there any discussion of possible military contributions by the Arab nations represented at the meeting.

Whether the Arab governments, which must often contend with significant segments of their populations who sympathize with the goals of militants like Osama bin Laden, will agree to the administration's request is an open question. Hints that Mr. Bush may have trouble holding together the coalition he envisions were not long in coming.

One of the envoys who met with Mr. Powell, Nabil Fahmy, the ambassador from Egypt, warned the administration that it must focus on finding and punishing those responsible for this week's attacks, and not broaden the effort to include other geopolitical goals.

He said the international coalition that waged the Persian Gulf war in 1991 ・which included Egypt and Syria ・worked because it kept to the clear objective of pushing the Iraqis out of Kuwait.

Hours before the session with the Arab diplomats, Prime Minister Ariel Sharon of Israel spoke to Mr. Bush, and according to officials, expressed skepticism about the United States' enlisting the aid of Israel's foes, Syria and the Palestinian Authority.

"If there is an attempt to bring Syria and Arafat into the coalition, then that is a problem," an Israeli official said.

Having spent a day attending a national prayer service in Washington and visiting rescue workers at the remains of the destroyed buildings in lower Manhattan, Mr. Bush was planning to meet with members of his cabinet and his national security advisers during the weekend at Camp David. The White House, taking extraordinary security measures, disclosed few details about the president's schedule over the next several days.

Unity was the theme on Capitol Hill as Congress moved with exceptional speed to express support for the president and provide funds for retaliation and reconstruction. Congress was appropriating twice as much as the $20 billion that the administration had asked for to start the antiterror campaign.

"These are different times," said the Senate minority leader, Trent Lott, Republican of Mississippi. "And we have got to act decisively. The American people expect it of us, and they will accept nothing less."

But some members of Congress also injected a note of caution into the administration's rapid-fire military and diplomatic campaign. The resolution authorizing military action was intended to give the president political support, but not unfettered power to wage war.

The joint resolution fell short of a full declaration of war, which lawmakers said would have been inappropriate in military action against a shadowy enemy.

The resolution states: "That the president is authorized to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on Sept. 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons."

Senator Joseph R. Biden Jr., chairman of the Foreign Relations Committee, said Congress was not ceding its constitutional authority to declare war or intending to write a measure like the Gulf of Tonkin resolution, which President Lyndon B. Johnson used in 1964 to justify escalation of the war in Vietnam.

The resolution specifically states that it does not supersede the War Powers Resolution of 1973, which requires the president to seek Congressional approval for any extended use of American forces in combat.