Summit for three?

HERE is an offbeat proposal that might help the course of US-Soviet relations over the next four years. Mikhail Gorbachev and Ronald Reagan should schedule the fifth summit meeting that is at present only a gleam in their eyes. They should schedule it before President Reagan leaves office, but after the November presidential election, when we will know who the next president is to be.

Mr. Reagan should take along to the summit meeting with Mr. Gorbachev whoever is to be the next president, whether that be George Bush or Michael Dukakis.

Right about now, I can hear the clamor of opposition, telling why this will not work.

From the White House schedulers will come the argument that it just isn't possible to schedule a summit between the November election and the President's departure from office in January, especially with Christmas in between. Well, what's the point of being president of the United States and general secretary of the Soviet Communist Party if you can't have your way on a little meeting now and then? We've seen Reagan and Gorbachev in forceful action together. If they want such a meeting, they can have it.

From the White House public relations people, one can expect the argument that a summit shared with the president-elect would demean Reagan's stature on the occasion of his last international hurrah. Why so? Would not he go down in history as the man who not only improved US-Soviet relations, but who also laid the basis for continuity of policy?

From the State Department may come the argument that a summit including a just-elected president could not be prepared in time. Well, Reagan and Gorbachev have proved that world leaders who want to slice through bureaucratic ponderousness can do business in a hurry when they want to.

From the State Department, too, may come the argument that there should not be a summit unless there are prearranged items for agreement. The next big item on the US-Soviet agenda - an agreement to cut back the big strategic nuclear missiles - may not have been negotiated, may not be ready for signing. Well, so what? There may be very good reasons for not rushing an agreement on START. But it would not be a bad idea for the next president to hear at first hand the discussion on where we are on START.

There are certainly other topics worth talking about: Afghanistan, Angola, Nicaragua.

Some foreign policy experts might argue that including the president-elect in a Reagan-Gorbachev summit could create disunity on the American side. Mr. Dukakis, for example, would be less ideologically tuned to Reagan than would Mr. Bush. But in the first place, the president-elect, who would not yet have been sworn into office, would be there as a high-level observer, not a negotiator. And in the second place, the whole point of this exercise would be to underline bipartisanship and continuity, not to smash it up.

Would Bush or Dukakis accept an invitation? Surely Bush would. And how could Dukakis, invited to get an early jump on his relationship with Gorbachev, refuse?

The advantages of such a three-man summit seem considerable. Gorbachev would get to know the president-elect, and the president-elect would get to know Gorbachev, without waiting for all the reappraisals and position papers that get written when a new US president assumes office.

The new president would know at first hand where the outgoing president and Gorbachev had left the state of the US-Soviet relationship. Beyond style and personality, the three-man summit could make a major contribution to what both sides say they want in the relationship - continuity in policy.