Soviet leader Mikhail Gorbachev arrived here today pledging to seek "positive results" in his meetings with President Reagan at the first U.S.-Soviet summit in more than six years.

Gorbachev's arrival from Moscow completed the preparations for what is being described on both sides as the most unpredictable meeting of the leaders of the world's two rival superpowers in more than two decades.

Gorbachev, who said Wednesday that he will "not go empty-handed" into the talks, was reported by Soviet sources to be bringing new proposals -- which could include surprises -- in the arms control field. The sources refused to give details, although there were hints that the proposals could involve weapons cuts greater than the 50 percent reduction already put forward by Moscow.

U.S. national security adviser Robert C. McFarlane told a press conference today that he knew of no new signals from Moscow on the eve of the talks, which begin Tuesday morning.

But several U.S. officials here indicated privately that they did expect new Soviet proposals. These officials also said the United States was prepared to respond if Reagan deemed it necessary. They said virtually the entire major U.S. policy-making group in arms control was on hand here in case rapid evaluations were needed.

The Soviet leader's spare, almost cryptic arrival remarks, which included an unusually vague reference to his government's strong opposition to Reagan's Strategic Defense Initiative, did little to clarify Moscow's public position going into the two days of talks.

In the months of presummit maneuvering both nuclear superpowers offered dramatic -- but very different -- proposals to cut their vast strategic offensive arsenals in half.

A senior U.S. official raised the possibility today that Reagan and Gorbachev would be "most likely to agree" to recall their arms negotiators to the Geneva arms control talks earlier than the planned Jan. 16 resumption date in an effort to break the current deadlock.

In previous sessions of the talks, there was little movement toward closing the gulf between the two sides on the crucial question of the U.S. antimissile defense program, popularly known as Star Wars, which the Soviets insist must be halted before any agreement on the offensive weapons cuts that both sides say they want.

Reagan, in a brief exchange with reporters on a day devoted to rest, a ceremonial appearance with Swiss President Kurt Furgler and final preparations, indicated that he will seek to persuade Gorbachev that the missile defense plan is a boon to mankind rather than the first-strike threat that Moscow describes. When SDI is "explained" to Gorbachev, said Reagan, "he'll find that [it] can help us end the arms race."

McFarlane said Reagan approaches the summit with "a deep sense of responsibility" and a determination to "tell it like it is" about the Soviet military buildup and "subversion."

Gorbachev disembarked from a Soviet airliner with his wife Raisa amid a dusting of snow on a gray, unseasonably cold day.

In his arrival statement, Gorbachev also spoke of the two leaders' responsibility to the peoples of their two countries and the rest of the world who "expect positive results from the Geneva meeting."

Indicating the priority he accords an arms agreement, Gorbachev said that the "first and foremost" question to be discussed with Reagan is "what can be done to halt the unprecedented arms race in the world and its extension to new spheres."

Gorbachev's use of the latter phrase rather than the usual Soviet warning against "an arms race in space" was termed "kind of interesting" by McFarlane.

Soviet Foreign Ministry spokesman Vladimir Lomeiko, however, later warned reporters against "drawing conclusions solely on the basis of a single word" and reiterated Moscow's opposition to SDI.

White House spokesman Larry Speakes spoke of "certain grounds for optimism" about the summit outcome. Soviet sources spoke in a slightly more optimistic tone following Gorbachev's arrival but added that they do not know what will happen or even how to judge whether the meeting is a success or failure.

U.S. officials said there have been no meetings between officials of the two sides since Reagan arrived here late Saturday.

A Lomeiko press conference, another in the active Soviet public relations effort here, was undermined by Irina Grivnina, a vociferous recent emigre from Moscow whose presence caused the Soviet spokesman to walk out of a large and crowded hall.

Lomeiko later continued in a much smaller room. The press credentials of Grivnina, here on behalf of a Dutch publication, were lifted by Swiss authorities. She also had disrupted a Soviet briefing yesterday.

Gorbachev's team of advisers for the summit, his first encounter with an American president, followed him off the plane and filed in behind him during the airport welcoming ceremony.

The team, including the official Soviet summit delegation, represents a mix of Gorbachev recruits to the Kremlin inner circle and seasoned experts on the United States.

One of the new faces was that of Eduard Shevardnadze, the 57-year-old Georgian who replaced Andrei Gromyko as foreign minister in July. Shevardnadze, a foreign policy novice, conducted much of the presummit legwork in two trips to the United States during the past eight weeks and several meetings in Moscow with U.S. Ambassador Arthur A. Hartman. The other new adviser was Alexander Yakovlev, a former Soviet ambassador to Canada who recently was named head of the Soviet Central Committee's propaganda department.

The familiar group of American specialists in the delegation included: Anatoliy Dobrynin, 66, U.S. envoy in Washington for 23 years; Georgi Korneiko, deputy foreign minister, formerly at the Soviet Embassy in Washington, and Andrei Alexandrov-Agentov, 67, a speechwriter, linguist and Kremlin foreign policy adviser since the early 1960s.

The other member of the delegation, Leonid Zamyatin, has been spokesman for the past four Kremlin leaders and is a former head of the Soviet news agency Tass. While awaiting Gorbachev's arrival in an airport lobby this morning, he appeared to be putting the final touches on remarks that the Soviet leader was to make later during a ceremonial appearance at a reception given by the Swiss president.

The experience represented in the group of Gorbachev's American specialists ranges wide. Dobrynin, one of the architects of the detente period, has wielded power and forged friendships among American politicians, journalists and businessmen for more than two decades.

Yakovlev, an English speaker, is known among westerners in the Soviet capital for his harsh views of current American politics, revealed in his recent book, "On the Edge of the Abyss, From Truman to Reagan." American Kremlinologists link Yakovlev to many of Gorbachev's critical assessments of the Reagan administration that the Soviet leader has expressed in private conversations with Americans, including Secretary of State George P. Shultz.

Conspicuous by his absence among the Kremlin delegates today was Gromyko, 74, ushered upstairs to the post of president of the Supreme Soviet last July, in a move that signaled to western analysts an end to an era of Soviet-American relations. As former ambassador to the United States and Soviet foreign minister for 28 years, Gromyko molded a foreign policy that was focused largely on the United States.

Gromyko participated in all previous postwar summits between U.S. and Soviet leaders. He laid the early groundwork for the Gorbachev-Reagan talks in meetings with Reagan in Washington in September 1984, and with Shultz here in January of this year.

But his role in preparing Gorbachev for this week's encounter with Reagan has been limited, according to Soviet sources.

Also conspicuously absent from the official Soviet delegation is a senior arms control specialist, Nikolai Chervov. An arms specialist on the Soviet general staff, he is in the Soviet party, but he is not a member of the official delegation. However, western diplomatic sources here have speculated that Yuli Kvitsinsky, a member of the arms talks negotiating team here, will appear before week's end.

Gorbachev appeared in an upbeat mood in both his morning arrival and afternoon reception ceremonies.

At the beginning of his call on the Swiss president this afternoon, Gorbachev stood next to Furgler, while a band blared out the Soviet and Swiss national athems and the flags of both countries flapped nearby in the crisp wind.

On arriving this morning, he smiled and shook hands with Swiss officials at planeside. Following his remarks, he was rushed off in a black Soviet Zil limousine to a villa at the Soviet mission, where he will stay until he returns to Moscow Thursday.