The only traditional diplomatic negotiating that went on at the summit meeting involved the contents of the joint statement that was issued in the name of both leaders Thursday morning.

The task of drafting the statement fell to a working group of mid-level officials from both countries, who first took up the task at 9 p.m. Tuesday, the first day of the summit, and did not finish it until they had met three more times, hammering out the final wording at about 4:30 a.m. Thursday.

As is often the case, this diplomatic attempt to describe what had been accomplished became the focus of debate about several of the central issues, particularly those involving arms control.

The U.S. team that worked out the statement combined officials who have often been at odds in Washington discussions of Soviet-American issues. It was headed by Assistant Secretary of State Rozanne L. Ridgway and included, at various times, Assistant Secretary of Defense Richard N. Perle, National Security Council officials Jack F. Matlock Jr. and Robert E. Linhard, and Deputy Assistant Secretary of State Mark Palmer.

On the Soviet side, the team included Alexander Bessmertnykh, chief of the U.S. department of the Soviet Foreign Ministry, Soviet chief arms negotiator Viktor Karpov and Oleg M. Sokolov, the second-ranking official of the Soviet Embassy in Washington.

Until the last predawn session resolved outstanding issues, American participants reported yesterday, the outcome was uncertain. Regular phone calls from Bessmertnykh to Soviet leader Mikhail Gorbachev helped the proceedings along, they said, but agreement was finally reached only after both sides had threatened not to go through with the planned closing ceremonies of the summit.

Serious differences surfaced almost at once in the discussion of the joint statement, ranging from the description of new forms of cultural exchanges to a general statement about nuclear strategy. But arms control was the most contentious matter.

The U.S. proposed draft guidelines for a section on arms control endorsing the idea -- previously advanced by both sides in differing forms -- of 50 percent reductions in offensive arms; encouraging movement toward a separate Soviet-American accord on intermediate-range missiles based in Europe; recognizing that work on strategic defensive systems such as President Reagan's "Star Wars" plan could continue within the confines of the 1972 Treaty on Anti-Ballistic Missiles; and endorsement of the principle of effective verification of any new arms agreements.

The Soviets rejected this idea, proposing instead to restate the communique both nations issued Jan. 8 outlining current arms control talks and calling for accords on intercontinental and medium-range weapons and for steps to prevent an arms race in space.

The final statement combined both approaches. It listed three of the four American points, but made no mention of defensive weapons such as those envisioned in Reagan's Strategic Defense Initiative, and did speak of preventing an arms race in space.

The Soviets urged that the statement speak of the "inadmissability of nuclear war." The U.S. team saw the Soviet language as suggesting a policy of "no first use" of nuclear weapons, which Washington has long rejected. The Americans instead put forward language Reagan has used, that "a nuclear war cannot be won and must never be fought." The Soviets gave way on this point, while the United States went along with the Soviet desire for a statement in which both sides agreed not to seek "military superiority".