IS THE COMPROMISE resolution on the Marines in Lebanon in trouble in Congress? Possibly. Last Tuesday, the administration and the congressional leadership of both parties accepted a compromise initially proposed by Speaker O'Neill: Congress would pass a joint resolution asserting that the War Powers Act applies, but also authorizing the president to continue deploying the Marines in Lebanon as part of a multinational force for another 18 months. On Wednesday the House Appropriations Committee-- normally prone to accept executive leadership in foreign policy--voted 20-16 to cut off funding for the Marines in Lebanon unless the president certifies by Dec. 1 that the War Powers Act applies--a certification that would give him 60 more days to get Congress to approve the deployment. On Thursday the House Foreign Affairs Committee approved the O'Neill resolution by a 30-6 vote, and on Friday its Senate counterpart, after some vote switching, did the same by a 9-7 margin. What is going on?

Everyone expects the Republican Senate ultimately to approve the resolution. The question is what the Democratic House will do when the resolution comes to the floor this week. The speaker will likely allow votes on amendments, and, while most people expect the leadership to prevail, some respected legislators favor the Appropriations Committee result.

Many members are uneasy. They would like the president to acknowledge more explicitly the legitimacy of Congress' role. Some want to put pressure on him to withdraw the Marines soon. Some believe that any set period, long or short, is dangerous because it might give one or another of the Lebanese parties an incentive to refuse to reach agreement; by delaying invoking of the War Powers Act until Dec. 1, they hope to give the president a chance to move the parties to agreement without setting any specific deadline now. The monkey of responsibility in any case would remain on the president's back. But could Congress, when the 60-day deadline starts Dec. 1, set conditions or promote discussions any more deftly than it can now?

We think the approach of the leadership compromise is better. It does invoke the War Powers Act. It forces Congress--including the Democratic House --to join the president in taking responsibility for a policy about which everyone has qualms but for which few have a palatable alternative. No one so far has come forward with a resolution calling for withdrawal of the Marines now. The danger is that the House will indulge too far the politician's instinct for compromise by cutting the 18-month leeway period to six or nine months. This would weaken, rather than strengthen, the American hand in negotiations, and could involve Congress in a series of fractious disputes over a policy that most members, if they had to take the responsibility directly, would almost surely support.