Key members of Congress, while still expressing overwhelming, bipartisan support for President Bush's response to the crisis in the Persian Gulf, are growing increasingly edgy about the prospects of a prolonged, ill-defined and still highly dangerous mission shouldered primarily by U.S. armed forces.

Lawmakers from both parties said a key test of whether the United States can maintain public support and meet its objectives of an Iraqi withdrawal from Kuwait and restoration of Kuwait's legitimate government would be the extent of multinational military cooperation, particularly by moderate Arab states.

But this concern, voiced early in the day by members of Congress, appeared to be largely met later yesterday when 12 members of the Arab League agreed to contribute ground troops to a multinational military force to protect Saudi Arabia.

In the strongest expressions to date of congressional concern, House Armed Services Committee Chairman Les Aspin (D-Wis.) called on Bush yesterday to more clearly define the overriding U.S. objective in Saudi Arabia.

In a letter to Bush, Aspin also urged the president to more clearly define the threat to U.S. economic interests posed by an intimidated Saudi Arabia. Even the restoration of the Kuwaiti government and the removal of Iraqi troops, said Aspin, could leave Iraqi President Saddam Hussein with the ability to dictate oil policy in the region.

"If our direct interests are not understood," Aspin wrote, "the public will be more likely to see as acceptable proposed compromises that do not permanently remove Saddam Hussein's ability to intimidate the government of Saudi Arabia into adhering to his oil production and pricing desires."

The Arab League decision to commit troops will make it harder for Saddam "to make it a holy war," said Sen. Joseph R. Biden Jr. (D-Del.). He said the United States should now slow deployment of its troops and put renewed emphasis on working with the Arab League and the United Nations.

"Our effort ought to be aimed at our allies," said Rep. Mickey Edwards (R-Okla.). "Since when did it become our role to be the sole defender of the Saudi Arabian oil fields?"

Other lawmakers said they expect Saddam to try and exploit a lack of U.S. patience for a prolonged deployment, but predicted that the American people would recognize the vital U.S. stake, in part because Saddam is such a clear and unpredictable danger.

The United States, said Sen. David L. Boren (D-Okla.), chairman of the Senate intelligence committee, faces a stern test that "could very well determine the extent of American influence in the post-Cold War world."

Predicting that Saddam would employ terrorism to test U.S. resolve, Boren said the nation faces a potentially "defining watershed event."

"If we have to go it alone, it will be a strain on our patience," Boren said. "But even if we have to do the lion's share, there's a real difference here; we just don't have a choice."

In addition to the threat of terrorist acts, lawmakers are still deeply concerned over Saddam's other wild cards -- the thousands of U.S. citizens under his control in Baghdad and in Kuwait, and fear that he will be willing to use chemical weapons against U.S. troops.

Rep. Robert G. Torricelli (D-N.J.), a member of the House Foreign Affairs Committee, said the United States should make it crystal clear it will regard any chemical attack as the "moral equivalent" of using tactical nuclear weapons.

Though Torricelli stressed his continued support for the Bush administration policy, he said the "mounting ambiguity" caused by the slow response of other nations has made the situation more dangerous and raised the risk of Arabs making this a "crusade against the American invader."

So far, said Torricelli, the military expedition is "about as international as the World Series."

But other members of Congress were more sanguine. Rep. Dave McCurdy (D-Okla.) said the gulf crisis presents the United States with a rare opportunity to "drive {moderate Arab states} into our camp . . . . In the long term it's an opportunity for people to choose sides."

While predicting a crisis that will last months, Rep. Jim Leach (R-Iowa) said public support for the Bush policy can be sustained. "Pocketbook issues are more unifying than ideological ones," he said. "The American people are growing more aware of the risks."

Though many lawmakers said the danger of hostilities with Iraq was most acute in the first few days, they still warn that a costly confrontation is possible.

"I think the hope is that {economic} sanctions take hold and we get the U.N. flag up rather than the U.S. flag," said Rep. Patricia Schroeder (D-Colo.). "If this thing breaks, this is going to be very costly in blood for anyone on the ground in Saudi Arabia."