The United Nations trade embargo against Iraq is showing the first signs of strain, with several U.N. members suddenly asking whether they are barred from sending food to Iraq and Iraqi-occupied Kuwait.

U.N. sources say that so far, there is evidence that only Jordan, Libya and Yemen are sending some food and other supplies to Iraq despite the U.N. Security Council's Aug. 6 call for sweeping economic sanctions against President Saddam Hussein's government.

But several other nations, among them Iran, China, India, Tunisia, Yugoslavia and Romania, say they are considering resuming food shipments. Some of these countries say they are motivated by desire to help their citizens caught in Iraq and Kuwait; some say that their economies are being damaged by inability to sell food exports to Iraq, and some say that including food in the trade boycott runs counter to their humanitarian beliefs.

The U.N. sources stress that the rifts over the food issue have not reached a point where the embargo is in danger of breaking down. But, the sources added, a closed-door meeting Thursday of the Security Council's sanctions committee was unable to agree on a mechanism for determining when food shipments are warranted. Instead the committee sought to buy time by asking Secretary General Javier Perez de Cuellar to collect more information about the effects of the embargo.

Those countries wanting to send food say that is permissible because the sanctions resolution exempted from the embargo "supplies intended strictly for medical purposes, and, in humanitarian circumstances." To withhold food shipments, they argue, could expose people in these countries -- particularly children, the sick and the elderly -- to malnutrition or even starvation.

However, the United States and its allies on the council counter that the "humanitarian" provision applies only to what one Western diplomat called "food donated and distributed by recognized international organizations in situations where humanitarian relief genuinely is required."

These countries say that while the embargo may be causing some shortages in Iraq and Kuwait, there is no evidence that conditions in either country have reached a point requiring such relief. U.S. and other western officials agree that medical supplies are exempt from the embargo, and they acknowledge that it might become necessary later to consider selective food aid, such as food for infants. But, they add, giving a blanket go-ahead to all food shipments would undermine seriously the embargo's effectiveness.

"In our view, the sanctions were put on to have effect," a senior U.S. oficial said yesterday. However, he added: "It is also clear that the Security Council has judged the object of this action is not to starve the people of Iraq to death.

"We believe no country can decide for itself when humanitarian circumstances exist," the official continued. "We believe the sanctions committee should determine when humanitarian circumstances apply . . . and any shipments should be handled through humanitarian agencies not governments . . . . This is particularly important in light of statements by Iraq that it will attempt to divert any food resources first to the army, then next to Iraqi citizens and last to the citizens of foreign countries."

Ambassadors of other countries on the Security Council made clear that opinions about food shipments cover a very broad range.

Ambassador Ricardo Alarcon de Quesada of Cuba, an implacable foe of the United States who abstained when the sanctions were voted, said: "There is a fundamental human right to receive a normal allowance of basic foodstuffs. People don't need caviar or champagne, but we are thinking in terms of milk and bread."

Colombian Ambassador Enrique Penalosa said he does not think allowing some food into Iraq would weaken the embargo because "the critical goods in the case of Iraq is not foodstuffs; it's oil."

Acting Soviet Ambassador Valentin Lozinsky pointed to the needs of "special groups like children" and said, "It's a hard question. The population should not be subjected to famine or starvation. On the other hand, sanctions have to have some effect."

Also yesterday, the U.N.'s attention was focused anew on the Security Council's Military Staff Committee because of indications that it might figure in Sunday's Helsinki summit discussions between President Bush and Soviet President Mikhail Gorbachev. On Thursday, Soviet foreign ministry spokesman Gennadi Gerasimov said Gorbachev might raise the idea of sending a U.N. military force to the gulf, and he recalled that the U.N. Charter makes the Military Staff Committee responsible for planning and supervising military activities undertaken under U.N. auspices.

The committee's titular members are the top military commanders of the Security Council's five permanent members: the United States, the Soviet Union, Britain, France and China. In practical terms, they are represented by military attaches, and the committee has been moribund throughout its 45-year existence.

However, in the negotiations leading up to the Security Council's Aug. 25 resolution authorizing the world's navies to enforce the embargo, the Soviet Union and many Third World countries wanted the military committee to run the operation.

But the United States, Britain and France wanted to retain control over their own forces and the council finally authorized military action without a U.N. flag or U.N. command and control. The resolution designated the military committee as a clearinghouse through which countries should report their Persian Gulf naval activities to the council.

U.S. and U.N. sources said yesterday that the Soviets, who two years ago said they would put the United Nations at the center of their foreign policy, appear intent on pushing the idea of building up the Military Staff Committee so it could run future U.N. military operations.

The sources said the Soviets do not appear to be insisting on such a role for the committee in the current gulf crisis, but want to build the committee's powers in gradual stages over the next few years.

Special correspondent Trevor Rowe contributed to this report from New York.