MIAMI BEACH, Fla. - John Gates, a former American Communist Party leader convicted of plotting to overthrow the U.S. government, has died at age 78, his wife said yesterday.

Gates died Saturday at the Miami Heart Institute. He had heart disease and had suffered a stroke.

Gates was the chief editor of the party newspaper, the Daily Worker, and one of seven national party secretaries until he broke with the party in 1958 after losing a campaign to democratize it.

He was one of the party leaders convicted in the nation's first Communist trials for plotting to overthrow the government and spent five years in prison. Gates denied the charge and said he was always a loyal American.

After his release from prison, Gates lobbied for reform within the party, saying it should split from Moscow's Communist Party and concentrate on working peacefully against injustices in the capitalist system.

"The ideals that attracted me to socialism still motivate me," his resignation letter said. But "the Communist Party has ceased to be an effective force for democracy, peace and socialism."

He worked for the International Ladies Garment Workers Union before retiring to Florida in 1987.

Born in New York City, Gates joined the Communist Party at age 17. He then moved to Ohio to mobilize jobless youths.

He fought in the Spanish Civil War, becoming commissar of the anti-fascist Abraham Lincoln Brigade at the age of 24. He was the highest ranking American in the war. He later enlisted in the U.S. Army and served in Europe during World War II.

He is survived by his wife, Lillian, a brother, and three sisters.