The United States must ultimately use power to back up its foreign policy, Sir John C. Slessor, Marshal of the Royal Air Force, declared yesterday.

At an open meeting of the Defense Studies Program, Slessor said, "Unless the United States can find some way to bring her power to bear throughout the world, she will lose her place as leader of the West."

Slessor stressed that direct power should only be applied after all economic and moral pressures have failed to accompish a given policy.

The British air commander criticized any policy based strictly on moral grounds as very dangerous. A simple moralistic foreign policy, according to Slessor, "just doesn't have enough flexibility."

Talking about the present crisis in the Middle East, which "could explode at any time," Slessor said President Eisenhower had given Israel a "promissory note." He felt that either the U.S. must "face up to this responsibility" to guarantee the rights of Israel, or she will lose great prestige among the Arab nations and around the world. Slessor also noted that "the Suez and the oil it carries is absolutely vital to the European economy."

Advocates Power in Middle East

He suggested several ways of implementing his "power policy." If the United States would place one of her "fat, sleek, new cruisers" in the Gulf of Aqaba, there would be little chance of the Egyptians trying to stop Israeli shipping, he said. He also felt that a U.S. destroyer could safely lead an Israeli freighter through the Suez. These steps should only be taken if all other diplomatic measures failed, however, he pointed out.

In an interview before his speech, Slessor indicated that the one hopeful place in the international picture is in central Europe. The recent revolts in Hungary and Poland, instigated by the supposedly completely indoctrinated youth, in an encouraging sign of "unconquerable human beings," he stated.

Slessor offered several steps that the West might take to achieve final international stability. First among these would be to give the UN something to do. He suggested letting the UN control all international waterways, and produce and market oil. Slessor also suggested that three "interlocking mutual security treaties, backed by the major powers," be firmly established in Europe, the Middle East and Asia.