UNITED NATIONS, AUG. 24 -- Diplomatic pressure against Iraq escalated as the U.N. Security Council appeared ready tonight to adopt a resolution permitting U.N. members to use military action to enforce trade sanctions against Iraq.

A breakthrough came this evening after nearly a week of negotiations among the five permanent members of the council when the Soviet Union said it would withdraw its objections and support the U.S.-backed initiative.

In hopes of winning an international stamp of approval for military action to stop violations of the U.N. trade embargo against Baghdad, the United States had lobbied hard for a Security Council resolution that would allow the use of "minimum force." But negotiators switched to less precise language today, agreeing that "measures commensurate with the specific circumstances" would be permitted in enforcing the embargo. The change was an effort to win over nations opposed to specifically allowing the use of force.

U.S. officials said the resolution's new wording would give individual nations more latitude in deciding whether, or how, to use force in enforcing the embargo.

A provision was also added calling for the "maximum use of political and diplomatic measures" to enforce the sanctions on Iraq and occupied Kuwait. The Soviet Union had been arguing that further diplomacy should be employed to resolve the crisis, but Soviet President Mikhail Gorbachev earlier today issued an ultimatum to Iraqi President Saddam Hussein, signaling that the Kremlin was planning to drop its objections to the resolution.

Calling the situation "extremely dangerous," Gorbachev warned the Iraqi president that the Security Council would be forced to take "appropriate measures" if Baghdad failed to abide by earlier resolutions demanding an Iraqi withdrawal from Kuwait and the release of thousands of Western hostages in Iraq and Iraqi-occupied Kuwait.

Tonight, the acting Soviet ambassador to the United Nations, Valentin Lozinsky, announced to reporters that the Soviet Union was ready to support the resolution. "Our intention is to vote 'yes,' " Lozinsky said after several hours of meetings with diplomats of the permanent council members.

In arguing for the resolution, the United States cited what it said was evidence of violations of the embargo. White House spokesman Marlin Fitzwater, with President Bush in Kennebunkport, Maine, today, expressed strong concerns that critical arms shipments and chemical warfare equipment were reaching Iraq despite the trade embargo.

An administration official said that Jordan was the source of at least some of the "leakage" in the embargo, including the shipment of arms, but other sources said the allegation of chemical warfare equipment reaching Iraq was directed at Libya.

In addition, reports from Yemen said Iraqi planes were in the Yemeni capital, Sanaa, to fly foodstuffs to Baghdad in defiance of the trade embargo, and Iraqi oil tankers were reported to have docked in Yemen and were being unloaded.

Libya and Yemen, after initially refusing to condemn the Iraqi invasion of Kuwait, have said they would support the economic sanctions. The Jordanian government of King Hussein, which has expressed some sympathy for Saddam, has also said it would support the sanctions.

The Soviet Union and some of the non-permanent members of the Security Council had objected to the draft resolution earlier in the week, saying that more time for diplomacy should be allowed and demanding a detailed definition of how the United Nations would control military operations to enforce the embargo.

Some nations had accused the United States -- which fired warning shots this week at two Iraqi tankers in a vain attempt to get them to stop and be searched -- and Britain of acting without proper Security Council authorization in trying to enforce the embargo.

The United States, along with France and Britain, had sought an arrangement that would give a U.N. stamp of approval to the naval interdiction forces those countries are deploying in the Persian Gulf region and would allow each country to maintain control of its own enforcement and rules of engagement.

During the days of talks, diplomats played with different wording on the issue. According to sources, the five ambassadors from the permanent members of the Security Council -- the United States, the Soviet Union, China, Britain and France -- each were in separate rooms of the French mission here tonight, with open phone lines to their capitals in an attempt to work out language acceptable to each other and to Third World countries on the council.

For approval, the resolution must have at least nine votes on the 15-member council. China, which has been opposed to the massive military buildup in the gulf and whose reluctance to support the measure reflected that of a number of Third World countries, was expected to abstain, although hopes were being held tonight by U.S. offficials that China might support the resolution.

Among the non-permanent members of the council, it was expected that Cuba, whose ambassador has attacked the United States for "Rambo tactics" in the crisis. Yemen was expected to either vote against the measures or abstain. Malaysia was considered another possible no vote, but its diplomats' intentions were uncertain this morning. It was not clear what the other countries would do.

The action here at the United Nations came amid other efforts in the region to ease the escalating crisis in the gulf.

Jordan's Hussein returned home from visits to Yemen and Sudan in order to receive Austrian President Kurt Waldheim, who flew to Amman today en route to Iraq on Saturday. Waldheim, the first Western head of state with plans to visit Iraq since the crisis began, was expected to press Saddam for the release of Western hostages and for permission for Austrian citizens to leave.

Waldheim, who has been isolated from nearly all democratically elected leaders because of his World War II past, undertook the diplomatic mission despite concern by Austrian Chancellor Franz Vranitzky that the visit would serve Saddam's propaganda aims.

Jordanian officials would not disclose the substance of Hussein's brief Arab tour, but politicians here said the Jordanian monarch was seeking to coordinate a common stand among the nine Arab countries that refrained from rebuking Saddam earlier this month at an Arab League summit conference in Cairo.

Jordan and a number of other countries have complained that enforcing the trade embargo is causing them severe economic problems. Tonight, White House officials were trying to complete an emergency aid package for Jordan, Egypt and Turkey to deal with the substantial economic hardships incurred by those nations as they cut off trade with Iraq.

Other nations were expected to contribute to the aid package, including Kuwait, Japan and Saudi Arabia. Aid to Jordan would be on the condition that Amman end an intelligence-sharing agreement with Iraq, close the port of Aqaba to Iraqi-bound shipping and strictly adhere to the trade embargo, according to one official involved in the discussions between Washington and Amman.

In a related development, Italy, acting on behalf of the 12-nation European Community, is expected to ask the Security Council to consider urgently the situation in Kuwait, where Iraq is threatening possible forcible closure of foreign embassies. The council already has declared Iraq's annexation of Kuwait "null and void" and has demanded that Iraq take no action against foreign diplomatic missions in Kuwait City.

Correspondents David Remnick in Moscow and Nora Boustany in Amman contributed to this report.