Senate leaders last night were at work on a plan to bar spending of $988 million in production funds for the MX missiles until Congress agrees on a final basing plan.

But they still had not worked out one important element in the compromise, and planned to resume discussions today.

The While House, fearful that the Senate might concur with the House and deny the production request, agreed to a plan under which the MX funds would be kept in the 1983 defense appropriation, but could not be spent until Congress agreed to a final basing plan for the missile. The White House wanted to add a provision requiring Congress to vote on the basing issue by May 1, and MX opponents were balking at such a requirement.

"I have not budged," said Sen. Ernest F. Hollings (D-S.C.) who met with Majority Leader Howard H. Baker Jr. (R-Tenn.), Majority Whip Ted Stevens (R-Alaska), Senate Armed Services Committee Chairman John G. Tower (R-Tex.) and other administration supporters yesterday. Hollings said he still has the votes for his plan to deny funds for the missile until Congress approves a bassing method.

"The administration is scrambling around trying to join our amendment and save face at the same time," he said. "They're playing games and trying to act like they're wheeling and detaining. But all of us are holding firm."

A four-page "compromise proposal," submitted by Tower and other administration supporters, was close to Hollings' original plan. It would have left MX procurement funds in the 1983 defense appropriations bill, but with the proviso that the money could not be spent until both houses of Congress agreed on where and how to base the missiles.

Unlike the Hollings amendment, the administration plan would have set a March 1 date for recommending a basing plan to Congress. Congress would then have until May 1 to vote on the plan. Debate in the Senate would be limited to 50 hours under an expedited procedure to prevent filibusters.

That proposal represented a major concession by Tower and other administration supporters who originally pressed for a plan to allow the spending automatically unless Congress blocked it by a certain date.

The Dense Pack basing plan is the most controversial issue now surrounding the MX. Under Dense Pack, 100 missiles would be buried in closely spaced underground silos in Wyoming.

Critics, labeling the plan "dunce pack," have ridiculed the theory that it would be protected from Soviet attack because incoming Russian missiles would be destroyed by their own blast.

Yesterday Sen. Mark O. Hatfield (R-Ore.), a long-time opponent of the missile, said he would not accept a time limit for deciding on a new basing plan, and hinted he might filibuster the basing issue if and when it reached the floor next spring. Noting that he would like to kill the missile, he said, "I see no reason to set a date for the decision.... I want to preserve the right to talk extensively...."

Stevens said negotiations were not over. "We'll have a refined draft tomorrow. We have a general understanding."

A fast track decision on the 1983 funds is necessary, he said, because by next spring Congress will be voting on the 1984 budget.

Whatever is worked out in the Senate must be approved in conference with the House whose position is to cut production funds unconditionally. The Senate is likely to vote on the MX issue as part of a stopgap 1983 funding bill, since there is little time left in the lame-duck session to pass a separate defense bill.

House and Senate are in agreement, however, on spending $2.5 billion for MX research and development, part of which would be used by the Pentagon to reevaluate Dense Pack. "Dense Pack would appear to be dead, looking at it from a practical standpoint," Sen. Charles H. Percy (R-Ill.) said yesterday.