HELSINKI, SEPT. 9 -- President Bush and Soviet President Mikhail Gorbachev today warned Iraqi President Saddam Hussein that they are prepared to take additional steps if sanctions fail to force Iraq to retreat from Kuwait, but they differed over whether military force might eventually be needed to resolve the Persian Gulf crisis.

While Bush left open the possibility of military confrontation, Gorbachev made clear that the Soviet Union is skittish about the potential for combat and wants to find a political solution. Bush pressed Gorbachev to remove military trainers from Baghdad. Gorbachev said the number of trainers is being reduced, but did not promise to evacuate them immediately.

The two leaders of nations that were once bitter enemies issued an unprecedented joint declaration condemning Iraq for its invasion of Kuwait. This followed seven hours of talks here that were dominated by the confrontation with Saddam.

"Nothing short of a return to the pre-Aug. 2 status of Kuwait can end Iraq's isolation," they said. "Nothing short of the complete implementation of the United Nations Security Council resolutions is acceptable." They called for Iraq to pull out of Kuwait, restore its "legitimate government, and free all hostages held in Iraq and Kuwait."

The leaders declared that they want to end the crisis "peacefully," but said, "We are determined to see this aggression end, and if the current steps fail to end it, we are prepared to consider additional ones consistent with the United Nations Charter."

American officials said these steps could include further sanctions against Baghdad, sanctions against those nations that break the global embargo against it, a tightening of the blockade by stopping air traffic into Iraq, and other measures including, ultimately, the use of force under the collective security provisions of the U.N. Charter.

Bush and Gorbachev appeared to leave open the possibility that the economic embargo of Iraq could be relaxed to allow humanitarian shipments of food if monitored by international agencies to ensure that such aid "reaches only those for whom it is intended," particularly children. {Related story, A19.}

Although Gorbachev committed the Soviet Union to the unspecified additional steps envisaged by the joint statement, he did not otherwise advance the Soviet position beyond its previous endorsement of the U.N. sanctions against Iraq and its call for a full withdrawal. He stopped short of any move to join the multinational force now being deployed in Saudi Arabia or expanding the Soviet role in the naval bloackade. Asked if there would be any further Soviet military participation in the area, he replied, "I don't see the point of doing that now."

But displaying pique at Saddam, Gorbachev called on the Iraqi leader to show "sobriety" and said, "What the present Iraqi leadership is doing is driving into a dead end."

According to a source familiar with the details of today's discussions, Gorbachev made clear to Bush that he has little sympathy for Saddam, describing him as "brutal" and "cruel" and talking about him in much the way that Western leaders have. Gorbachev said Iraqi Foreign Minister Tariq Aziz was told not to come to Moscow unless he had new proposals to make for resolving the crisis, but when he came last week, he brought nothing new, irritating the Soviets, the source said.

Saddam's televised appeal to Gorbachev to break with the world community on the eve of the summit also irritated the Soviets, this source said. At the same time, Gorbachev said he wanted to exhaust all diplomatic options before even contemplating any military action, the source said.

"They are quite prepared to sign up to put the squeeze on Saddam Hussein," said the source. "But they are not keen on using military force."

Secretary of State James A. Baker III told reporters that "there was never an approach to us by the Soviets today that we want you to forswear that option" of military force. Baker said the military option is "open not just by omission" but is explicitly left open in the joint statement threatening to take additional steps, as long as they fall under the U.N. Charter.

At the press conference, Bush said he and Gorbachev "did not discuss military options," and that the "question was too hypothetical." He added, "I would like to see this matter peacefully resolved." But when asked later about contrasting U.S. and Soviet views on the use of force, he acknowledged, "We may have a difference on that."

In the private talks with Bush and a later meeting that included aides, Gorbachev raised no objections to the massive U.S. military deployment in Saudi Arabia, now involving 100,000 troops, except to ask how long it would remain, the source said. In a remark designed in part to reassure Gorbachev, Bush said at the press conference that he told the Soviet leader "that we have no intention" of keeping the forces in Saudi Arabia "a day longer than is required." Bush said, "The sooner they are out of there, as far as I'm concerned, the better."

Seizing on Bush's statement that the United States has no intention of leaving American forces in the region, Gorbachev said, "That's a very important statement."

However, in congressional testimony last week, Baker suggested that the United States might have a long-term naval role in the gulf, noting that U.S. ships have been there since World War II. Baker said the ships may be required as part of a broader regional security arrangement.

Elaborating today on Bush's public comments, National Security Adviser Brent Scowcroft also indicated that U.S. troops might remain in the gulf even if Iraq withdrew its forces from Kuwait. Bush, Scowcroft said in an interview on NBC, "didn't say we would pull out as soon as Saddam Hussein withdrew, but he wouldn't keep them there a day longer than necessary. I think that what we have to see is the implementation of a security system in the gulf which will guard against a simple renewal of the conflict."

In recent weeks, U.S. officials have held out little hope of a quick pullout given Saddam's enormous military machine and the threat he poses to others in the region. Gorbachev, however, has been under pressure from military leaders who are worried about such a large U.S. deployment so close to Soviet borders.

Citing Moscow's close cooperation at the United Nations in the global effort to isolate Saddam, Bush offered his most positive assessment yet of the prospect for economic aid from the United States to the Soviet Union. Bush said he would recommend to Congress "as close cooperation in the economic field as possible." While reminding Gorbachev of the U.S. budget deficit and other "constraints," Bush did not repeat his earlier demand that Soviet economic reforms must be complete before any American aid could be provided. Bush said, "There are many ways that we can endeavor to be of assistance to the emerging economy in the Soviet Union."

Gorbachev, while welcoming this gesture, said that the Soviet Union cannot "be bought for dollars" and that Moscow is being driven by a desire to be a full participant in the world community.

In a manifestation of that new role, Gorbachev -- suggesting that he was letting out a secret -- said Bush had told him the United States has dropped its long-standing objections to the Soviet Union's playing a role in broader Middle East issues. The United States has been moving in that direction in recent months. Baker said, "It's old thinking to talk about not inviting the Soviet Union to the Middle East."

Just three years ago, the United States was trying to keep Soviet influence out of the gulf. Back then, when Kuwait approached Soviet officials about protecting its tankers, the United States rushed in to reflag the Kuwaiti vessels -- expressly to keep the Soviets out.

Bush initially invited Gorbachev for a quick meeting in Helsinki for a display of solidarity against Iraq, which has a long-standing relationship with Moscow. To a large extent, this solidarity was evident in the comments of the leaders. Gorbachev said, "We have confirmed the most important progress of recent times."

The Soviet president described the Persian Gulf crisis as a historic test for the United States and Soviet Union, which invested large sums confronting each other in Europe and in Third World regional hot spots during the Cold War years. Gorbachev said he and Bush began their talks "realizing that the whole of world society and our two great states are undergoing a trial. This is a test of the durability of the new approach to resolving world problems."

But the difference of opinion over possible combat was also on display. Gorbachev emphasized repeatedly his desire for a "political resolution" and said the Soviet Union stood ready to use its good offices with Arab nations and others such as China and India to get a diplomatic resolution, but he did not elaborate. A military confrontation would "draw us into consequences which we can't at this stage forecast," he said.

Gorbachev said, "If Iraq were to provoke military action, then the result would be a tragedy first and foremost for the Iraqi people themselves, for the whole of the region and for the whole of the world."

A senior U.S. official said that despite these statements the administration believes Gorbachev's view of the crisis is an "evolving process" and would now require a period of emphasis on diplomatic activity, which has so far not borne results. "They genuinely want to pursue a diplomatic track," the official said. "They want to see if it can be fruitful. They want to see if all the options are exhausted. They have told Saddam, you have put yourself in a corner, and we're not going to help you get out."

On the general issue of international arms control, the two reaffirmed a desire to make progress on treaty negotiations to limit conventional forces in Europe and strategic nuclear weapons, but they appeared to be facing obstacles on both. Soviet Foreign Minister Eduard Shevardnadze said the goal of completing the strategic arms treaty by year's end "probably won't work out." Baker said major disagreements remain over limits on aircraft in the conventional forces negotiations.

Gorbachev said at the news conference that the economic embargo against Saddam "is a very stiff measure" in response to the invasion of Kuwait. He called this a "strategic way of tackling the question," and stressed the importance to world leaders of finding "the next stage" of a political settlement. "I have no doubt that we shall succeed in resolving the problem by political means," he said.

On the Soviet role in the Middle East, Bush said "under certain circumstances" he could support the long-standing Soviet call for an international peace conference on the region. But he reiterated that the United States does not want to link this to the current gulf crisis. Bush said he wants to see Israel withdraw from the occupied territories, as stipulated in U.N. resolutions, but he said the gulf crisis, sparked by "naked aggression" against Kuwait, should not be tied to "some other unresolved dispute." Israel contends there are major differences between the two situations and that it acted in self-defense.

While Bush drew no link between the Arab-Israeli dispute and the gulf crisis, Gorbachev said there was such a connection. "It seems to me there is a link here because the failure to find a solution in the Middle East at large also has a bearing on the acuteness of the particular conflict we've been talking about here," he said.

Bush said the issue of the Soviet military trainers in Baghdad "is not a major irritant." He said he told Gorbachev that "this was a question that was widely being raised in the United States and it would facilitate things if they were out of there in terms of total understanding."

In the joint statement, the two leaders also said that as soon as Iraq has pulled out of Kuwait, released all hostages and restored Kuwait's government, they would urge their foreign ministers to "develop regional security structures and measures to promote peace and stability." Baker had suggested in his congressional testimony last week that such steps include a new alliance of Arab nations involving the United States that would contain Saddam and block his quest for weapons of mass destruction.

"It is essential to work actively to resolve all remaining conflicts in the Middle East and Persian Gulf," the statement said. "Both sides will continue to consult each other and initiate measures to pursue these broader objectives at the proper time."

Bush later returned to Washington and Gorbachev to Moscow. Baker is scheduled to report on the summit Monday to NATO foreign ministers. In Moscow later this week, Baker and representatives of the four victorious World War II powers -- France, Britain, the United States and the Soviet Union -- are to sign a document with leaders of the two Germanys terminating four-power responsibilities over Germany. But Baker said tonight in an interview with Cable News Network that there is still an unresolved issue, which he would not specify.