A large shipment of Soviet military equipment, including planes, tanks and an advanced type of air defense missile, is expected to arrive in Syria later this month, informed diplomatic sources in Damascus said yesterday.

Reuter quoted the sources as saying that the missiles were a revised version of the SAM-6 which proved extremely effective when used by the Arabs in the 1973 Middle East War.

Military experts said the new missiles have an improved guidance system capable of overcoming jamming techniques developed by the Israelis.

The sources said the Soviet Union had approved sale of the new weapons to bolster Syria's defenses following Egypt's peace initiative with Israel.

"With Egypt apparently dropping out of the confrontation, Syria feels dangerously exposed to any military threat from Israel," one source said.

Syrian President Hafez Assad, meanwhile, criticized U.S. support for the peace initiative undertaken by President Anwar Sadat of Egypt. In an interview with Newsweek senior editor Arnaud de Borchgrave, Assad said: "The U.S. is comfining its own moves and role to the framework of Sadat's initiative. That's obvious to any observer and not at all helpful if the aim is to bring about a comprehensive settlement."

Assad also attacked the use of the word "rejectionist" to describe the group of Arab nations opposing Sadat's action.

"It was the front of Arab steadfastness," he said. "We decided not retreat in the face of the Zionist offensive and to persevere because the moves now taking place in the region embody a comspiracy against the Arab nation with the objective of imposing its capitulation."

Sadat lashed out at once of his critics today during a news conference in Khartoum during a visit with Sudanese President Jaafar Nimeri. The Egyptian leader denounced President Houari Boumedienne of Algeria for aligning himself with those states criticial of his peace moves.

Sadat returned yesterday to Aswan, Egypt, where he is to meet with the shah of Iran. Over the next two weeks Sadat will receive visits from King Hussein of Jordan, King Hassan of Morocco and British Prime Minister James Callaghan, all of whom have spoken out in support of Sadat.

In Amman, Jordan, a spokesman for King Hussein announced he would be visited Tuesday by President Boumedienne, who is on a tour of key Arab capitals.