The Navy is "putting increased emphasis" on operating its submarines under the ice in northern waters to counter the "strong interest" of the Soviet Union in hiding its submarines there, the chief of naval operations said yesterday.

The ice-covered coastal waters of the Soviet Union are "a beautiful place to hide" submarines, Adm. James D. Watkins said, adding that the Navy must be better prepared to find them there and, in a war, be ready to sink them. He said that the United States dare not let the waters under the ice become a "sanctuary" for Soviet subs.

Watkins, while confirming Soviet interest in hiding submarines under the ice, did not say Soviet missile submarines are lurking there. But he said that the Navy must do more to prepare itself to operate in that perilous environment, calling it "a whole new ball game."

U.S. submarine crews are receiving more training under the ice, and their subs are getting special equipment, such as steel covers for the conning towers and other parts of the submarines that would be the first to push through a thick layer of ice.

For submarines the icy depths are "a very special environment, a very noisy environment" when it comes to trying to identify the sounds heard by sonar operators while the subs are prowling the depths, Watkins said.

One problem, he continued, is that when the ice is thick "there is a very small separation" between the ocean floor and the bottom of the ice. Another is that a submarine could move through a canyon under the ice and end up unable to turn around.

In an emergency, it might be necessary to punch through the ice to reach the surface, said Watkins, who commanded a nuclear attack submarine before becoming the nation's top sailor.

Some of the Navy's attack submarines are "hardened" for such ice breaking, Watkins said. Ones now under construction will be specially equipped for under-ice operations, he added. Besides extra steel protective layers, submarines operating under ice require special software for their computers and navigational devices.

The Soviets put a high premium on protecting their missile submarines, Watkins said. For both the Soviets and the Americans, the intercontinental ballistic missiles hidden in submarines are "the ace in the hole" for deterring nuclear war, for negotiating an early end to a war and for retaliating if all else fails, he added.

Watkins said that under the ice is a logical Soviet operating zone. "It's clearly an advantage to them to take their ice that is heavy most of the year around their homeland and use their forces accordingly."

Watkins declined to discuss whether Soviet ballistic submarines would be the prime wartime target for U.S. killer submarines. He said, "All I'm saying is that if there are forces up in that area of the world" where there is ice under which to hide, "we'd better know how to fight them."

He said that the United States is still several years ahead of the Soviets in submarines but that they are making significant strides. Watkins said that to stay ahead, the Navy next year will ask Congress for money to start building a new class of missile submarines in 1989. The new sub would be larger than the Los Angeles-class attack subs now patroling the deep, he said.

In discussing other topics, Watkins distanced himself from Navy Secretary John F. Lehman Jr. on the question of whether Navy carriers and other warships would sail into the teeth of the Soviet defense around the Kola Peninsula in a war. Lehman has said that the Navy should be prepared to do this.

While praising Lehman, Watkins said that Lehman is in the "administrative" chain of command, not the operational one that decides where each ship goes in an emergency. Watkins saw aircraft carriers as protecting the vital sea lanes in a war, not "charging off" to the Soviets' back yard, where they could be attacked by Soviet land-based aircraft. The Navy secretary, he said, "does not set operational strategy."