President Bush yesterday expressed support for a French proposal to expand the international trade embargo against Iraq to include air interdiction, but officials said the White House prefers a system that would penalize nations whose aircraft land in Iraq and not involve the use of force to stop planes.

At a news conference, Bush said he wants to "tighten up" the United Nations sanctions to stop air deliveries that violate the sanctions, adding, "I would be prepared to work with anybody to tie that additional knot in sanctions."

An administration official said while the White House has not promoted the concept of air interdiction, Bush wants to "show solidarity" with France, which is pressing for it. Bush was briefed on the status of the sanctions at a Cabinet meeting yesterday by Thomas R. Pickering, the U.S. ambassador to the United Nations.

The president also dismissed concerns over Iran's renewal of diplomatic ties with Iraq and statements by Iranian clerics criticizing U.S. action in the gulf. "We have had indirect assurances from Iran that they want to see these sanctions complied with and enacted. . . . Until I am shown that Iran is violating the sanctions, I'm not going to buy into the argument they've made some secret deal to violate the sanctions," he said.

Asked about U.S. contacts with Iraqi President Saddam Hussein before the Iraqi invasion of Kuwait, Bush acknowledged that the United States sent no strong signals warning Iraq of the consequences of invasion and said that "with hindsight" he "absolutely" regrets this.

These questions arose because of recent accounts of a meeting in late July between Saddam and U.S. ambassador to Iraq April C. Glaspie in which the ambassador did not directly answer Saddam's threats of an invasion. Bush and others repeatedly have said that they did not believe Iraq would invade Kuwait, and viewed the massing of Iraqi troops on the border as pressure aimed at forcing Kuwait to bargain.

Bush said that, until the invasion, "there was some reason to believe that perhaps improved relations with the West would modify {Saddam's} behavior." But he added that regardless of the events leading to the invasion, "I don't think this is caused by a miscalculation in United States' policy. I think it's caused by a miscalculation by Saddam Hussein. And I think the American people understand that to a fare-thee-well."

The president also responded to recent concerns in Congress and elsewhere over the potential diminution of U.S. military authority in the multinational force still being assembled in the gulf. "We're not going to have to stand around waiting for someone else to decide if there is a provocation either," Bush said. He said the command structure involves extensive consultations with commanders from other nations and with the host country but also places fundamental reliance on the U.S. commander in the gulf, Army Gen. H. Norman Schwarzkopf.

Bush refused to predict whether public support for his gulf policies would continue if fighting breaks out and American lives are lost. Saying he is old enough to remember World War II, Bush said that while there was "a lot of sorrow" over American casualties, "the country stayed fairly well together."

Administration officials have expressed little enthusiasm for expanding the Iraq embargo to include aircraft, arguing that few planes carrying little cargo were reaching Iraq. Officials cited what one called "a lot of dangers" potentially involved in air interdiction that are not involved in sea interdiction.

"If the French want this embargo, we would support the concept," said a senior official, but the administration would push for an alternative to outright shooting planes down such as "third-party sanctions." Under such a system, a country that flew aircraft to Iraq without authorization would not be allowed to land its planes anywhere else the sanctions are being observed.

According to the official, the United States is uncomfortable with the concept of challenging a plane when "you either stop it or you don't, there's no show-me-your-cargo step" as there is with shipping at sea.

At his news conference, Bush also repeated his opposition to using the Strategic Petroleum Reserve until the country is clearly threatened by an oil shortage. But for the first time he indicated some interest in drawing down a small amount of the reserve to discourage price speculation. Such an argument, he said, "has some appeal."

In a related development, Congress yesterday approved and sent to Bush a bill authorizing the free mail already begun from U.S. military personnel in Saudi Arabia. The House approved 368 to 0 the bill allowing them to mail letters, cards and audio cassettes home without postage. The Senate had approved the bill by voice vote Friday.