A meeting of North Atlantic Treaty Organization defense ministers that saw pressure build for an interim proposal on nuclear missiles in Europe wound up here today.

U.S. Defense Secretary Caspar W. Weinberger and NATO Secretary General Joseph Luns indicated, however, that it would be some time before such a proposal is forthcoming.

Luns, who on the eve of this conference had called Reagan's pending zero option proposal "not attainable," today said it would be two months before the president could submit a different one to the Soviets, if he chooses to do so.

The zero option calls for the Soviets to retire their entire force of SS20 and other medium-range missiles in exchange for the United States' forgoing the planned deployment of 108 Pershing II and 464 cruise missiles in Western Europe.

Luns said today that "the reason I expressed some doubts" about the viability of the zero option "was the completely negative attitude of the Soviet Union." He added that "there might be an interim solution which would finally, we hope, lead later to the zero option."

If there is an interim proposal, said Luns, "it can obviously only be made" after the new round of U.S.-Soviet missile negotiations reconvenes in Geneva. The current session is scheduled to recess next Tuesday and reconvene 60 days later.

Weinberger is expected to put up a fight against any sudden switch from the zero option when he returns to Washington Friday. After the talks here, Weinberger flew to Madrid for talks with Spanish officials.