Surrounded by Soviet generals and winking computer lights in a nuclear bomb-proof bunker, Defense Secretary Dick Cheney got an unprecedented look at the Soviet Union's air defense system Thursday.

He was taken 65 feet underground at a secret base on the outskirts of Moscow and led through nine steel doors to a large room lined with radar-display wall maps of Europe and the Soviet Union.U.S. officials said it was the first time Westerners had seen the control room of the Moscow Air Defense Center, one of nine guarding the vast Soviet land mass from air and nuclear attack.

"Interesting. Impressive," Cheney said after he and a group of U.S. defense officials and reporters traveling with him were shown the center on the third day of a rare Soviet visit.

He was briefed by Defense Minister Dmitry Yazov and other generals and was told the center controlled at least 300 interceptor jets as well as anti-aircraft missiles.

Cheney watched from a long table laden with computer screens and banks of telephones while maps on the wall were changed electronically to show Moscow, all of the eastern Soviet Union and Western Europe.

Among those answering Cheney's questions was Gen. Ivan Tretyak, who took over Soviet air defense in a shake-up after West German Mathias Rust sneaked unseen past the defense network in 1987 and landed his small plane next to Red Square.

Soviet officials said the command post, hardened by concrete and its floors and ceilings lined with steel, was built in the 1950s to withstand a nuclear blast.

Cheney later flew to Tula, south of Moscow, to watch the training of elite Soviet airborne troops. He will fly to Paris Friday after a joint news conference with Yazov.