Gen. Albert C. Wedemeyer, a noted American military planner and commander in World War II, died Sunday at Fort Belvoir, Va. He was 92 years old and had been in declining health.

The general died at the Belvoir Woods Health Care Center, a retirement community at Fort Belvoir where he moved earlier this year, his son Albert D. Wedemeyer said. He previously lived for years on a farm in Montgomery County, Md.

General Wedemeyer was ''one of the most intellectual and farsighted military minds America has ever produced,'' John Keegan, a military historian formerly at the Royal Military Academy at Sandhurst, wrote in The New York Times in 1987.

The general was a protege of Gen. George C. Marshall, Chief of Staff of the United States Army during World War II. He served as a staff officer under General Marshall and then became commander of American forces in China late in the war. He subsequently played a prominent role in the postwar evolution of American policy toward China. Role in World War II

A highly regarded career officer, the future general joined the Plans Group of the War Plans Division of the War Department General Staff in 1941. His assignment was to formulate an overall war plan for the United States. That plan, after the Japanese attack at Pearl Harbor, was the basis of the American war effort.

Advancing rapidly in the Army, he became a general officer and an important man in overall strategy. He went on most of General Marshall's trips abroad and played a major role in Allied strategy in the Mediterranean and in the planning for the Normandy invasion.

In 1943 General Wedemeyer was named as American deputy chief of staff to Adm. Lord Mountbatten, the British head of the Southeast Asia Command. When the general became the commander of the United States-China Theater in the next year, he simultaneously took the post of chief of staff to Generalissimo Chiang Kai-shek, the Chinese Nationalist leader, replacing General Joseph W. Stilwell as the generalissimo's closest military adviser.

General Stilwell lost the support of Lord Mountbatten and General Chiang when he urged General Chiang to incorporate Chinese Communists into the war against Japan.

General Wedemeyer, although he initially said he would not interfere in Chinese politics in any way, ultimately become intimately involved in the tortuous political and military developments in China as the war came to an end.

The general was remarkably successful in working harmoniously with Chiang and in training, equipping and paring the scattered and poorly organized forces of Nationalist China. Together with Chinese headquarters, he had prepared an offensive designed to recapture much of the South China coast from the Japanese. But the war ended, making the move unnecessary. Strains on China Policy

General Wedemeyer's attitude toward General Marshall cooled when his old chief was Secretary of State in the Truman Administration. General Wedemeyer differed with the Administration's China policy, favoring stronger intervention in support of Chiang than did Administration leaders. He blamed General Marshall's lack of understanding and the United States lack of a postwar China policy for the deliverance of the Chinese mainland into Communist control.

His special knowledge of Chinese affairs led to his being sent in 1947 as head of a mission to investigate the situation in China and Korea. General Wedemeyer's report was so controversial that it eventually led to his retirement from military service for a career in business.

The report called, among other things, for an American-led South Korean force strong enough ''to cope with the threat from the north.'' It was not made public at the time, and the general charged that President Harry S. Truman had suppressed it.

When the report was released in 1951, the general, having already applied for retirement, testified at Senate hearings, but his testimony appeared to confuse senators and neutral observers as to where he stood.

Albert Coady Wedemeyer was born July 9, 1897, in Omaha, the son of Capt. Albert Anthony Wedemeyer, an Army bandmaster in the Spanish-American War. He graduated from the United States Military Academy, held a variety of posts and studied Chinese on an assignment in Tientsin, China, in the early 1930's. Military Studies in Berlin

In 1934 he entered the Command and General Staff School at Leavenworth, Kan. Two years later he graduated with such high honors that he was chosen to attend the Kriegsakademie in Berlin - the General Staff School.

He returned to the United States in 1938, it was said, with a suggestion of his tutors' ''monocled aplomb.'' He turned in a report on the German military mind and machine. It was read by General Marshall, who was assistant chief of staff of the War Plans Division of the War Department General Staff at the time.

After the war, General Wedemeyer returned to the United States and was appointed deputy chief of staff for plans and combat operations at the Pentagon. After the China-Korea report, he became commander of the Sixth Army in San Francisco.

From that time on, he thought of himself as cut off from further military policy making, and consequently he retired in 1951 as a lieutenant general. In 1954 he received his fourth star by act of Congress.

After his retirement, he lived for some years on the Upper East Side of Manhattan and was an executive of the Avco Manufacturing Corporation and later of the Rheem Manufacturing Company.

In the 1952 Presidential campaign he was national chairman of the Citizens for Taft Committee, supporting the conservative Ohio Senator over Dwight D. Eisenhower for the Republican nomination.

He wrote the book ''Wedemeyer Reports'' in 1958.

He was awarded the Medal of Freedom by President Ronald Reagan and held other American and foreign decorations.

He is survived by his wife, the former Elizabeth Dade Embick, whom he married in 1925; two sons, Albert Dunbar Wedemeyer of Boyds, Md., and Robert Dade Wedemeyer of Arivaca, Ariz.; six grandchildren and nine great-grandchildren.

A funeral service is to be held at 11 A.M. today in the Fort Myer Chapel adjoining Arlington National Cemetery. Burial will be in the cemetery.

Albert Wedemeyer (1897)