"I can't tell you how glad I am to be back in the U.S.A.," John Denver told a breakfast gathering at the National Press Club yesterday. He then told everyone how glad he was to visit the U.S.S.R.

Denver, known in the streets of Moscow as "the environmental singer from the West," called his recent 12-day visit to the Soviet Union a "goodwill journey." He had no official status, though he did meet with a group representing the Soviet Union of Composers, which originally invited him. Denver is one of the few well-known American artists to visit Russia since the U.S.-Soviet cultural agreement expired in 1979. A new agreement is currently being negotiated.

The trip, Denver said, was "a heart-to-heart mission, a people-to-people initiative" with no political debate or discussion. His five concerts, two at Spasso House, the official U.S. residence in Moscow, were free; one show, for diplomatic children, had him second-billed to Kermit the Frog. "The people in this country are not the government and the people in that country are not the government. We want the same things," he said.

Though he traveled only to Moscow and Leningrad, Denver, 39, said he came away impressed with the Soviet people's "desire for peace." In Leningrad, he visited the cemetery where 600,000 victims of the 900-day siege in World War II are buried. "We lost 450,000 people in World War II, and I know what a loss it was to our country, how our people hold our experience and our memory of the Second World War. So it was a pretty astounding experience for me to visit a cemetery in which lie 600,000 people," Denver said. "The Soviets lost 20 million people. There's not a family in that country that was not touched by the war and, I'll tell you, these people want peace." The visit to the cemetery inspired a new (though yet unfinished) song titled "Have We Forgotten?"

Denver said he was surprised at the strong reaction to a number of songs about world hunger. As spokesman and chairman of National UNICEF Day, he recently visited Africa; he said that ending world hunger and working for peace have become personal priorities. Survival, Denver added, used to imply "you or me. But we've taken an evolutionary step and we realize that if we're going to survive on this planet, it's going to be you and me. Together we can make the world of peace that we've always dreamed about."

The trip was underwritten, to the tune of a quarter million dollars, by Pepsi, and most of it was filmed for a possible TV special. Denver met with a Soviet cosmonaut and attended a Bolshoi rehearsal and a Russian rock opera ("It could run for a few months on Broadway"). He toured the Hermitage Museum and went to Smolniy Institute in Leningrad, where he saw the famous picture of Lenin speechifying with his arm pointing outward. "That was pretty far out, I thought. Every day was full. I'm a tired cowboy."

Denver also visited the headquarters for Melodya, the official Soviet record company, and set up plans for recording with Soviet musicians, possibly next summer. In the Soviet Union, he said, there is "a great interest in Western music. They love rock and roll."