Secretary of State James A. Baker III says the Soviet threat to stop destroying its SS-23 missiles would violate an arms control treaty and appeared to be part of a publicity campaign to divide NATO.

The Soviets agreed to destroy the SS-23s, along with five other types of missiles, in the Intermediate-Range Nuclear Force Treaty that was signed in December 1987 and went into effect last June, said Baker."This is a matter that was specifically negotiated when the INF Treaty was negotiated," he said.

"The elimination of the SS-23s on the part of the Soviet Union . . . was debated back and forth for quite some time. The Soviets responded in effect that they would agree to eliminate these missiles, and now they are doing so," Baker said Sunday on the CBS-TV interview program, "Face the Nation."

Soviet Foreign Minister Eduard A. Shevardnadze, visiting Bonn on Saturday, warned that if Washington did not drop plans to modernize its short-range Lance missile, the Soviet Union would respond by developing a new short-range weapon or by retaining the SS-23s, which have a range near the 300-mile limit imposed by the treaty.

The Soviet Union has deployed the SS-23Spider since 1985 as a replacement to the 1960s vintage SCUD missile, and has about 75 Spiders in the Soviet Union and East Germany, according to the Pentagon. The INF treaty calls for the Kremlin to destroy all the SS-23s by October 1989.

The INF pact required the superpowers to destroy all missiles with ranges of 300 to 3,000 miles, but did not cover the Lance, which has a shorter range.

The United States has deferred until 1992 plans to modernize and replace the 88 Lance missiles it has in West Germany but has resisted West German and Soviet pressure to begin immediate negotiations on that class of weapons.