A Soviet deep-sea salvage ship is probing intensively in one spot west of Sakhalin Island, leading U.S. officials to think that the Soviets have found wreckage or believe they have found wreckage from the South Korean airliner they shot down Sept. 1.

U.S. officials said the Soviets have surrounded their salvage ship with warships and trawlers, making it difficult for U.S. Navy vessels in the area to see what is happening. They said the State Department may reiterate a U.S. request for international observers to be allowed on the Soviet vessels.

The United States, meanwhile, is close to calling off its search in the Sea of Japan for the airliner wreckage, knowledgeable officials said yesterday. The officials said a final decision will probably be taken by the end of this week to suspend searching after one more week, with increasingly unfavorable weather conditions to be cited as the reason.

The Soviet Union shot down Korean Air Lines Flight 007 almost two months ago, killing 269 people aboard the New York-to-Seoul flight. The Soviets charged that the jetliner, which had strayed into Soviet airspace, was on a spy mission, a charge dismissed by U.S. and South Korean authorities as ludicrous.

Almost as soon as the plane went down, U.S. and Soviet naval vessels began competing to find the wreckage and, in particular, the "black box" recorder that might provide information about the jet's movements during its last minutes. U.S. officials hoped such evidence would provide clues as to why the jet strayed off its designated route and how the Soviets shot it down.

The U.S. ships, aided by sonar, submersible cameras and sophisticated navigational equipment, searched a 14-square-mile area where experts believed the plane might have sunk. When that search proved fruitless, it was expanded to a 65-square-mile area west of Sakhalin.

That area too has now been exhaustively searched, Pentagon officials said. While they are restudying currents and other phenomena that might help pinpoint some positive sonar readings they picked up weeks ago, the officials have become increasingly pessimistic.

They have attributed their difficulties in part to interference from two dozen Soviet ships operating in the area. U.S. officials say those ships have shown lights to blind U.S. captains at night, forced U.S. ships off course by coming straight at them and, in at least one case, brandished guns at a Japanese vessel under lease to the U.S. Navy.

But the approaching winter is even more a limiting factor as the Navy moves toward abandoning its search, officials say. Earlier this week, U.S. ships had to cease efforts temporarily in five- to eight-foot seas, with 20- to 30-knot winds blowing rain and snow.

"Out of a three-day period, they're operating a total of eight hours," one official said. "They can't go on much longer."

Officials said the United States probably will abandon its search with another plea to the Soviets to allow international observers on their ships if the Soviets continue searching.

A State Department spokesman said late yesterday, however, that she knew of no plans to communicate with the Soviets on the subject.

That longstanding request took on new importance with intelligence reports of the concerted Soviet activity 14 miles north of Moneron Island. Initial reports said the Soviets were searching within their 12-mile territorial limit, where the Navy had not been permitted to search, but U.S. officials now say the Soviet vessel in fact has settled just outside territorial limits in international waters.

"The Russians have stopped and settled on this one spot, and they're shielding it with their combatants," one official said.

The search site is slightly to the east of the 65-square-mile area the U.S. vessels had combed.