A senior U.S. official held out the possibility today that President Reagan and Soviet leader Mikhail Gorbachev would be "most likely" to agree to call their negotiators back into an early session here in an effort to break the current deadlock on nuclear arms control.

Other senior officials cautioned that the idea, presented to a small group of reporters by someone close to arms talks, had not been formally discussed. But he said that it would give the leaders a chance for agreement and that both "want to come out of the summit with something."

It is known that during the third and just completed round of arms talks, the Soviet negotiators asked their U.S. counterparts to submit a proposal that both sides could agree to, either during the summit or shortly afterward. A U.S. official said the American side responded by making a proposal, the details of which he would not disclose, and that this proposal seemed to received by the Soviet negotiators positively. No formal Soviet reply was received before the talks recessed.

The arms negotiators -- who are discussing limits on strategic and intermediate-range missiles and bombers along with space defense systems -- are scheduled to resume Jan. 16. But the U.S. official said he expects Reagan and Gorbachev to agree on an earlier resumption to emphasize their concern for arms control.

The official acknowledged that the two sides are far apart on a new arms accord and said that simply agreeing to an early resumption ran the risk of appearing to be "cosmetic."

"I think what you're probably going to see come out of this is an agenda for a future summit," the official said.

Publicly, U.S. officials took a positive tone in advance of the two-day summit. Privately, they gave no sign that the United States expects anything except a frank dialogue and some minor agreements such as a new cultural accord, a North Pacific air safety treaty and an agreement on curbing nuclear proliferation.

White House spokesman Larry Speakes said, "The president believes that this can be a watershed meeting in which we hear each other out and begin to understand each other better. If the Soviets share our commitment to a fresh start, this meeting can provide the foundation for real enhancement of dialogue in all four areas of the meeting's agenda: arms control, regional issues, bilateral issues and human rights."

Robert C. McFarlane, White House national security adviser, said that Reagan "intends a comprehensive presentation on the strengths, values, purposes, goals of the United States looking to the end of the century. He will, as well, express the views of the United States of the Soviet Union . . . .".

McFarlane said Reagan would begin his presentation in his first private session with Gorbachev and denied, under questioning, that what he was describing as Reagan's approach sounded like a monologue rather than a more spontaneous give-and-take with the Soviet leader.

McFarlane said the first session Tuesday, which will begin with a one-on-one session between the two leaders, will be "vintage President Reagan."

"The president has prepared his own remarks," McFarlane said. "He will deliver those extemporaneously."

Some U.S. officials have expressed concern privately that such an extemporaneous approach presents a hazard to Reagan because of his penchant for verbal slip-ups.

On the other hand, a number of officials maintain that Reagan is often most effective in direct, personal discussions of the kind he will have for eight hours with Gorbachev on Tuesday and Wednesday. Both men will have the benefit of simultaneous translation during their discussions except for the first 15 minutes, when they will be alone with only interpreters present.

Reagan met today with Swiss President Kurt Furgler.

Seated with Furgler in a small library of the official government villa, the president answered a few questions, mostly about his missile defense program, the Strategic Defense Initiative. The SDI project, popularly called Star Wars, is at the heart of the central dispute at this summit. The Reagan administration is demanding cuts in offensive missile power, and the Soviets are adamant that there can be none if the United States proceeds with its defense shield that Moscow says could lead to a U.S. first-strike capability.

When a reporter mentioned Gorbachev's persistent opposition to the proposal, identifying it as "Star Wars," Reagan said, "I think when it's explained to him, he'll find that it can help us end the arms race."

When a reporter asked how, Reagan said, "Well, first by stopping calling it 'Star Wars' and calling it what it is -- a defensive shield, instead of an offensive weapon."

White House officials insisted in their public statements today that Reagan does not want to modifiy SDI, which Gorbachev says should be limited to "fundamental research" without testing or development of any defensive weapon.

"Anyone who has heard the president speak knows his position on SDI is firm and knows he will not bargain on SDI now or later," Speakes said.

But officials privately repeated statements they made Sunday saying SDI offers the prospect of a future trade for Soviet nuclear offensive weapons.

Secretary of State George P. Shultz, appearing on "CBS Morning News," declined to forecast the results of the summit, saying that "the crystal ball has so many fingerprints on it now that you can't see what's inside."

But Shultz rejected the notion that the United States would give the Soviets most-favored-nation trading status in return for their easing of emigration policy, calling "the notion of trading things for human lives" an "inherently repulsive idea."