Two Soviet warships are expected to pay a port visit to Mexico for the first time next month, U.S. officials said yesterday. The State Department expressed "concern" about the visit in a message to the Mexican government.

The planned visit is "significant," one official said, because until now Soviet naval deployments to the Caribbean Sea have included port calls only in Cuba.

"Obviously, we're concerned about the Soviet ability to move their ships in and out of the Caribbean," a State Department official said. "Mexico is an independent country and they can do what they want, but we have made our concerns known."

A Kashin guided missile destroyer and a Krivak guided missile frigate are expected to visit the eastern Mexican port of Veracruz Oct. 4, U.S. officials said. The vessels are now in the North Atlantic Ocean steaming toward the Caribbean.

A spokesman for the Mexican Embassy here, Ricardo Ramirez, said he had no information about such a visit and that the naval attache here also had not been informed.

"I don't know what the big concern is about," Ramirez said. "I know that American ships have been in Mexico, and European ships, many times."

The Reagan administration has expressed concern in the past about what it calls Soviet efforts to increase the U.S.S.R.'s influence in Central America and the Caribbean region.

"This is a brand-new thing we haven't seen before," the official said. "They have a blue-water navy now, and they're using it as you'd expect, for political presence."

Defense Department officials said that the Soviet navy has visited the Caribbean 24 times since it began conducting exercises there in 1969. Last year five ships -- three warships, an oiler and a submarine -- conducted exercises in the area, and the year before that, the Soviets sent a helicopter carrier to the area for the first time.

The Soviet ships ordinarily exercise with Cuban vessels and then steam into the Gulf of Mexico, not far from Texas or Louisiana, on what Navy officials call a "presence mission."