The Soviet Union has begun to dismantle its long-disputed Krasnoyarsk radar station in a bid to clear the way for a landmark strategic arms treaty, U.S. and Soviet officials said yesterday as negotiators met here to resolve arms issues in time for a joint statement by President Bush and Soviet President Mikhail Gorbachev later this week.

The Bush administration, like the Reagan administration, has said it will not sign a new strategic arms reduction treaty (START) until the Soviets dismantle the giant radar, which became a symbol of U.S.-Soviet discord after the United States consistently charged that it violated the 1972 Anti-Ballistic Missile Treaty.

Bush and Gorbachev hope to announce during this week's summit that they have settled all major issues blocking a START accord, which could be formally signed by the end of the year.

Gorbachev told Bush in a letter last September that the Soviet Union would take down the radar without conditions. About a month later, on Oct. 23, Soviet Foreign Minister Eduard Shevardnadze declared publicly that construction of the radar, which is 30 stories high, was "a clear violation" of the ABM Treaty.

Despite the public statements by Gorbachev and Shevardnadze, U.S. officials noted continuing controversy about the status of the radar in Soviet military circles.

A U.S. source said that only in recent days was there evidence that the process of dismantling the radar has begun. A senior Soviet official confirmed that destruction of the costly apparatus is underway, though he said he still retained hope that joint U.S.-Soviet operation of the radar could be worked out to avoid its total destruction.

Washington has been charging almost continuously since construction was first spotted in mid-1983 that the radar was a violation of the ABM Treaty because of its location and its capability to detect and track ballistic missiles. The Soviet Union, until recently, consistently denied it.

Shevardnadze said last October that it had taken the Soviet leadership four years of investigation "to sort out matters with this station" and establish "the entire truth."

A Soviet official said that the radar had been built to fill a large gap in that nation's early-warning system and that it was the fault of Soviet diplomats and negotiators that its construction at Krasnoyarsk in Siberia turned out to be a violation of the ABM accord.

Shevardnadze said the radar station had cost several hundred billion rubles, making it one of the most expensive Soviet construction projects in history, and would require a further investment to dismantle.

Gorbachev ordered construction of the radar halted in October 1987, after which the Soviets made several proposals to use the giant radar for space-related research, under Soviet or international auspices. The United States rejected all of the proposals.

A Soviet negotiating team headed by Deputy Foreign Minister Viktor Karpov met at the State Department for the second day yesterday with a U.S. team headed by Undersecretary of State Reginald Bartholomew. The teams have been trying to settle about a half-dozen substantive issues so Bush and Gorbachev can declare at their summit that all major strategic-arms questions have been solved.

The State Department said the teams had met for 6 1/2 hours in three sessions Sunday and an additional 2 hours 45 minutes yesterday. The meetings are to continue today, the State Department said.

Meanwhile, Bush said yesterday that, while Gorbachev has "enormous problems," he remains strong and nothing has occurred in the last few days to alter the dynamics of the summit that is to begin Thursday.

Questioned in Kennebunkport, Maine, as he concluded a round of golf, Bush said that, despite troubling reports of panic buying in Moscow and outbreaks of violence, "it's not our business as the United States to sort out the other person's economic problems . . . it is our business to understand them, to make clear to him what we can do and those things we can't do."

The president said that, in preparation for the summit, he was "taking a lot of time to try to assess the economic situation" in the Soviet Union. But one of the major advantages sought by the Soviets, a grant of most-favored-nation trading status, will "not be an action item" at the talks, he said.

The Soviets have not instituted immigration reform, one of the U.S. preconditions for granting enhanced trade status. Bush also linked an MFN grant to improvement in the status of Lithuania, noting that while more trade is "vitally important" to the Soviets, the status of the Baltics is "very important to us."

Bush, who said he has been reading two staff-prepared briefing books here in between golfing, jogging, fishing and boating, said he goes to the summit "with open arms to welcome the president of the Soviet Union."

The president resisted offering a public analysis of Gorbachev heading into the summit, saying, "I think we spend too much time trying to figure out how long a leader in any country will be there. I mean, this man has survived."

Bush said his "personal opinion is that he's pretty darn strong there, and I say that after talking to an awful lot of Soviet experts." Bush returned here late yesterday.

A Soviet official, speaking at a summit briefing for Washington reporters, predicted the summit would be productive despite concerns about developments in Moscow.

Nikolai Shishlin, an adviser to the Communist Party Central Committee, said that, "in spite of the pretty complex political background, this meeting is well prepared and has every prospect for success."

Asked about Gorbachev's strength in view of political challenges and turmoil at home, Shishlin said:

"For all the tumultuous political processes that are developing, for all the passions and emotions that are building up inside the country, for all the painful and crucial nature of the moment we are living through, the expansion of perestroika is proceeding . . . the position of Gorbachev at present is a strong position and a position of authority."