Kubinka Air Force Base, U.S.S.R. (AP) – U.S. Defense Secretary Frank Carlucci boarded the Kremlin’s new secret bomber and watched war games on tours Tuesday of two bases that had been off-limits to Westerners.

The visits to Kubinka including the bomber NATO calls the Blackjack, and to an army artillery division were unprecedented for an American official, Carlucci said later, but did not persuade him that the Soviets had moved from an offensive to defensive military posture.

“We, for example, have seen no change in force structure nor have we seen any change in the resources going into the Soviet military establishment,” he told a news conference back in Moscow. The Pentagon chief said he would continue seeking a 2 percent increase after inflation in the U.S. military budget.

During his visit to the air base 31 miles west of Moscow, Carlucci spent about 10 minutes in the cockpit of the long-range Blackjack bomber. Foreigners had seen it previously only in drawings and reconnaissance photographs.

Marshal Sergei F. Akhromeyev, the Soviet military chief of staff, inpected a B-1 bomber last month at Ellsworth Air Force Base outside Rapid City, S.D.

Soviety military officials were much more forthcoming to Carlucci than to foreign journalists about the sleek white plane with a sharply pointed nose.

They kept reporters and photographers behind a rope barrier about 50 yards from the plane and refused to tell them anything about it.

“Why do you want to know about the bomber? Why frighten people?” asked Carlucci’s host, Col. Gen. Boris F. Korolkov.

Korolkov, first deputy commander-in-chief of the Soviet air force, refused to identify the air-craft, whose only markings were a red star and a number of 12 on the tail.

“Soviet Military Power”, the Pentagon reference book, says the four-engine bomber is the world’s heaviest and largest but does not give dimensions.