Norwegian Prime Minister Kare Willoch said yesterday that he supports the U.S. "zero-zero" proposal to eliminate all intermediate-range nuclear weapons from Europe but added that he would support an agreement that might only be "close to this optimum."

Willoch made his comment in his departure statement after a morning meeting and lunch with President Reagan at the White House. An American official who briefed reporters after the meeting said Willoch did not specify to Reagan how many Soviet missiles either located in Europe or aimed at the continent he would find acceptable.

Reagan said he reassured Willoch of the U.S. resolve to maintain world peace by working with the North Atlantic allies.

"The most important current issue," Willoch said, "is the question of disarmament and arms control and in particular the Geneva negotiations. The western goal remains clear. We want to reach a balance of force in Europe with as few nuclear weapons as possible. The zero option with no intermediate nuclear weapons on either side is the optimum outcome.

"We know that the United States will make all possible efforts to get an agreement with the Soviet Union as close to this optimum as possible. To achieve this, it is of the utmost importance that the allies stand united."

On Thursday, after meeting with Defense Secretary Caspar W. Weinberger, Willoch told the National Press Club that if the Soviets reject the zero option the United States should be willing to continue to negotiate.

"Compromise may be necessary . . . in order to achieve something that is at least an improvement," he said.

The briefer informed reporters that Reagan told Willoch that U.S. negotiator Paul Nitze has been "instructed to explore any serious Soviet proposal . . . . Paul Nitze is not in chains."

While the only U.S. proposal calls for eliminating the entire class of intermediate-range missiles, the U.S. official said the president explained to Willoch that the United States "does not have a take-it-or-leave-it approach to negotiations . . . " Reagan wants the Soviets to understand that "the zero option is a realistic goal" for an arms control agreement.

In his press conference Wednesday, Reagan said that Vice President Bush heard expressions of support for the zero option from heads of state during his recent European visit, but that "there is no question, they wanted to know whether we are going to be willing to talk other issues . . . and he pointed out my orginal statement, and that has been our position. If somebody wants to present another offer, we will negotiate in good faith with this."

Reagan added that the most recent Soviet offer did not "sound to me like a reasonable proposal."

Reagan asked Willoch's opinion on the outcome of the coming election in West Germany and its effect on NATO alliance support for the zero option, but the U.S. spokesman gave no details on the Norwegian prime minister's response.

In his news conference, Reagan said that refusal by a newly elected West German government to deploy missiles in Germany would "be a terrible setback to the cause of peace and disarmament."

In addition to arms negotiations, Willoch said, he and the president discussed the Soviet effort to convince Europeans not to allow nuclear missiles to be based in Europe. The U.S. official said Willoch told the president that the western allies must do a "better job" of countering the Soviet line.