MANAMA, Bahrain (AP) _ The Soviet Union has increased its military presence in the Persian Gulf since the Iran-Iraq cease-fire, despite publicly urging withdrawal of foreign navies from the region, a U.S. military official said Thursday.

Gen. H. Norman Schwarzkopf, commander of U.S. forces in the gulf, said the Soviet navy continues escorting that nation's tankers while the United States and other navies have scaled back escort operations.

''I see no withdrawal of the Soviets in this area,'' Schwarzkopf told reporters. ''As a matter of fact ... I see an increase in their diplomatic initiatives... and their military assistance initiatives.''

Schwarzkopf said there has been a gradual reduction of U.S. forces in the gulf since an Aug. 20 cease-fire halted fighting in the eight-year war between Iran and Iraq.

The U.S. naval force in the gulf and the Arabian Sea now consists of 23 ships and will soon be cut to 19, Pentagon officials said. Schwarzkopf said the unit, which has operated in the gulf since 1949, would wind up slightly larger than the six ships in the region before mid-1987 when forces were boosted to protect U.S. shipping during the escalating war.

Schwarzkopf said Soviet Foreign Minister Eduard Shevardnadze, who visited Iraq and Iran on a recent regional tour, did not honestly state the number of Soviet ships in the gulf.

''I will tell you, without going into details, that his mathematics are very bad, compared to what we've seen here,'' Schwarzkopf said.

U.S. military sources say the Soviets maintain seven to nine ships in and near the gulf, including missile frigates and destroyers. The sources, speaking on condition of anonymity, said there has been no significant change in the Soviet force since the gulf war truce.

''The Soviets now have a permanent presence in the Arabian Gulf, that they've never had before,'' Schwarzkopf said. ''They have a very heavy presence of forces in the Red Sea, which, of course, Mr. Schevardnadze didn't talk about.''

He said the Soviets also had ''an overwhelming number of military advisers and military men'' in South Yemen - the only communist regime in the Arab world - in Ethiopia, Iraq and other countries, and have ''a very large troop presence'' just north of the Soviet-Iran border.