UNITED NATIONS, SEPT. 25 -- The U.N. Security Council, in a highly unusual meeting at the foreign-minister level, voted today to tighten the economic embargo against Iraq by cutting off air traffic to and from that country and Iraqi-occupied Kuwait.

Before the Security Council vote, Soviet Foreign Minister Eduard Shevardnadze, speaking to the General Assembly, lashed out at Iraqi President Saddam Hussein with the harshest language the Soviet Union has used since the start of the crisis, calling Iraq's actions "an act of terrorism" and "an affront to world order." While he stressed that his government still hopes Iraq can be induced by peaceful means to relinquish Kuwait, he made clear that if diplomacy does not work, Moscow might support some form of U.N. military action to force the Iraqis out.

Meanwhile, a 76-minute videotaped speech by Saddam, made in response to President Bush's eight-minute message delivered on Iraqi television 10 days ago, was broadcast in full on Cable News Network and in excerpts on other networks today. {Details on Page A30.}

Today's resolution -- the eighth passed by the Security Council since Iraq's invasion of Kuwait Aug. 2 -- also called on the United Nations' 159 member states to detain any Iraqi ships defying the embargo that enter their ports. It said the council will consider measures to punish countries that help Iraq evade the sanctions.

Fourteen of the council's 15 members, including the five permanent members -- the United States, the Soviet Union, China, Britain and France -- voted in favor. Cuba, which has accused the United States of using the crisis for imperialist aims, voted against.

In a symbolic demonstration of the seriousness with which the international community views the Persian Gulf crisis, all of the council members except Cuba and Ivory Coast were represented by their foreign ministers, for only the third time in the 45-year history of the United Nations. The U.S. seat was taken by Secretary of State James A. Baker III, and the meeting was presided over by Shevardnadze.

Later, following the Security Council vote, Baker said: "For international society to permit Iraq to overwhelm a small neighbor and to erase it from the map would send a disastrous message. The hopes of the world for a new, more peaceful post-Cold War era would be dimmed."

Stating that "our purpose must be clear and understood by all, including the government and people of Iraq," Baker said there can be no compromise with the council's demands, set forth in the earlier resolutions. They call on Iraq to withdraw from Kuwait, restore its legitimate government and release the thousands of foreign nationals it is holding as human shields against attack.

"If the United Nations is to fulfill its mission, if peace is to prevail, then Iraq's leader simply must not be allowed to gain from his assault on decency and basic human values," Baker said. "We must do what justice, honor and international peace demand: We must reverse Saddam Hussein's brutal aggression."

Today's resolution extends the ban on shipping to Iraq and Kuwait to air traffic. It calls on U.N. members to prevent Iraq-bound flights from taking off from their territory or to allow such flights to use their airspace. The only exceptions are flights carrying food "in humanitarian circumstances" authorized by the Security Council's sanctions committee.

The resolution also seeks, as Baker said, "to plug any loophole in the isolation of Iraq" by raising the possibility of punishment for countries that help Iraq and by authorizing the detention of Iraqi ships. An earlier resolution permits the United States and other countries with naval forces in the gulf to stop ships at sea suspected of carrying cargo to Iraq.

In his speech to the General Assembly, Shevardnadze referred to Aug. 2 as "that Black Thursday when Iraq flagrantly violated the United Nations charter, the principles of international law, the universally recognized norms of morality and the standards of civilized behavior."

"Iraq has committed an unprovoked aggression, annexed a neighboring sovereign state, seized thousands of hostages and resorted to unprecedented blackmail, threatening to use weapons of mass destruction," he added.

"An act of terrorism has been perpetrated against the emerging new world order," Shevardnadze said. "This is a major affront to mankind. Unless we find a way to respond to it and cope with the situation, our civilization will be thrown back by half a century."

He then delivered what delegates here interpreted as an unmistakable warning that Moscow is prepared to support the use of force against Iraq if the occupation of Kuwait cannot be ended by peaceful means.

"In the context of recent events we should remind those who regard aggression as an acceptable form of behavior that the United Nations has the power to suppress acts of aggression," Shevardnadze said. "There is ample evidence that this right can be exercised. It will be, if the illegal occupation of Kuwait continues."

He stressed, though, that the Soviet government believes that it is still premature to turn to military action and that diplomatic efforts to defuse the crisis should be continued. "Of course before -- and I reiterate, before -- this, all political, peaceful, nonmilitary forms of pressure must be applied to the aggressor, obviously in combination with economic and other enforcement measures," he said.

He also reiterated Moscow's view that any resort to force should occur under official U.N. auspices, and he renewed the call made by the Soviets last month to give the Security Council's Military Staff Committee a major role in planning and supervising military operations, under the U.N. flag.

Shevardnadze acknowledged that the committee, whose members technically are the armed forces chiefs of the five permanent council members, has been moribund during its 45-year history because "during the Cold War it could not and did not have a role to play."

The United States, Britain and France have taken a go-slow approach toward revitalizing the committee because they are unwilling to place the forces they have deployed in the gulf region under a joint U.N. command.

But Shevardnadze hinted that giving that kind of responsibility to the Military Staff Committee would be the price for Moscow's participation in any military ventures in the gulf. He said:

"The Soviet Union is prepared to conclude an appropriate agreement with the Security Council. . . . If the Military Staff Committee worked properly, if appropriate agreements had been concluded between the council and its permanent members, and if other aspects of countering threats to peace had been worked out, there would be no need now for individual states to act unilaterally."

A senior British official accompanying Foreign Secretary Douglas Hurd said that sometime between "now and Christmas, President Bush, in communication with his principal allies, will need to take stock of the situation."

The official, who spoke with reporters on condition he not be identified, said that if peaceful measures do not seem to be having the necessary effects, the West will have to consider other measures.

However, the official stressed, that does not mean the United States or its allies automatically would decide on military action. He said:

"At the present time, it is very difficult to measure and construct what might be done. I don't say {Bush} necessarily will be reaching a conclusion, but he would want to take stock. He might say, 'Let {the present reliance on sanctions} keep running for a while.' "

News services reported:

Syrian President Hafez Assad and Saudi Foreign Minister Prince Saud held talks in Damascus after Assad returned from a visit to Iran. A joint communique issued in Tehran after Assad's talks there called for an unconditional withdrawal of Iraqi troops from Kuwait as the first step in resolving the gulf crisis.

In Cairo, Iraqi Ambassador Nabil Negm Takriti said that forces from Arab countries could stay in Saudi Arabia on condition that Western and other non-Arab troops pull out.

Meanwhile, in the first fatal accident involving a Saudi citizen with American military personnel since the troop buildup began last month, a Saudi civilian was killed and six people, including four U.S. Marines, were injured in a two-vehicle collision on a Saudi expressway on Monday, U.S. officials said today. One of two Saudis injured was listed in critical condition.