W. Averell Harriman, the 87-year-old senior statesman and postwar presidential adviser on Soviet Affairs, came to the Kremlin today and talked of trade, nuclear war and Josef Stalin.

Addressing more than 400 Soviet officials and American businessmen gathered at the Kremlin Palace of Congresses, Harriman said that increased bilateral trade will help stabilize relations in an uncertain era, declaring it "an outrage that we do not have normal trade relations with the second-greatest country in the world."

Recounting anecodetes from his many meetings with Stalin over the years, Harriman called the Soviet dicatator a man of "extraordinary brutality," but one who "had a capacity for leadership and patriotism" that saw his country through the ravages of World War II, in which 20 million Russian died, to a rebuilt economy afterward.

Harriman, U.S. ambassador her from 1943 to 1946, and chief U.S. negotiator on the 1963 nuclear test ban treaty with the Soviets and British, recalled first meeting Stalin in 1926, when the New Yorker came here as a businessman seeking a manganese concession from the new Soviet state.

His recollections of Stalin, whose name has been almost erased from public discourse since his death in 1953, caused obvious consternation among the Soviets at the huge banquet. Some stared stonily at their plates. Others asked about their plates. Others asked about the weather in America. And some snorted in derison when Harriman quoted Stalin at the wartime Tehran Conference as saying the Soviet Union could not have defeated Hitler's armies without American lend lease aid.

But some listened with evident interest to the recollections of a man who had been there and could describe first hand what he had seen and heard without the filter of official historians to alter or distort.

Harriman said Stalin agreed at the conference to a Red Army offensive against the Germans on the eastern front to coincide with a cross-channel invasion by the Allies from England. He said Stalin later called the June 1944 invasion of Normandy "a grandiose operation," unrivaled in the history of war. Soviet dogma casts the Allied invasion in far smaller dimensions these days.

The diplomat is here as a special representative to the unofficial Trade and Economic Council, which groups about 300 U.S. companies with Soviet trading organizations. He said he does not think Soviet-U.S. trade should be linked with other aspects of Moscow-Washington relations such as strategic arms talks. The businessmen applauded this.

Harriman told his audience at the luncheon that he had just come from a 90-minute meeting with Leonid Brezhney and was convinced that the Soviet president does not want nuclear war with the United States.

"Those who say he's planning a first strike are paranoid," Harriman declared.