Defense Secretary Dick Cheney has quietly rescinded a nine-year-old ban on U.S. military personnel attending Soviet functions celebrating May Day and other occasions.

The decision, disclosed Tuesday by defense sources and confirmed by the Pentagon's chief spokesman, was announced in a memorandum dated April 27 that was distributed throughout the U.S. military.The memo states Cheney had lifted restrictions on attendance by Department of Defense personnel at Soviet receptions or other functions in the United States to mark May Day or Victory in Europe Day, imposed after the Soviet invasion of Afghanistan in December 1979.

Dan Howard, the Pentagon's chief spokesman, said the decision simply reflected the Soviet Union's recent withdrawal of troops from Afghanistan and nothing more.

A similar restriction on high-level State Department personnel was lifted in mid-February, according to administration sources. That was why U.S. Ambassador Jack Matlock viewed the May Day festivities in Moscow on Monday from the official diplomatic review stand - the first time that has been done in 10 years, the sources said.

According to Cmdr. Mel Sundin, another Pentagon spokesman, active-duty and civilian defense officials were specifically barred from accepting invitations to four key Soviet military observances - Soviet National Day in November; Armed Forces Day in February; May Day on May 1; and Victory in Europe Day on May 9.

The ban was imposed by the Carter administration just after the invasion and has been "rigidly enforced ever since," said one defense official.