The Soviet Union has apparently renewed its disinformation campaign in the Third World against the United States, despite recent pledges by top Soviet leaders to end it.

U.S. officials said a report last Saturday in the Ghanaian Times alleging the United States had given South Africa chemical weapons, which had been turned over to rebel groups in Angola and Mozambique, bears the imprint of a Soviet disinformation "plant."

The report alleged that South Africa was both obtaining chemical weapons from the United States and exchanging information on "bacteriological weapons" with American scientists at the Fort Detrick laboratory in Maryland.

State Department spokeswoman Phyllis Oakley said the United States "categorically denies all these ridiculous allegations and regrets that the Soviet Union has chosen to repeat them."

She said the State Department had no plans to protest to the Soviets over the report but added, "It will not be forgotten."

Charles Z. Wick, director of the USIA, said after the December U.S.-Soviet summit here that he had been assured by Soviet leader Mikhail Gorbachev and other Soviet officials that Moscow would end anti-American disinformation.

Wick, through a spokesman, said Friday that his office had told the Soviets that the chemical weapons report "was the kind of thing that undermines the move toward greater understanding between our two countries."

U.S. officials are particularly incensed by the report because it alleges that the United States is developing a biological weapon designed to kill individuals of a particular ethnic group or race. Similar reports of such a U.S. "ethnic weapon" have been circulated in Africa periodically over the last three years.

The report was picked up Jan. 9 by the Soviet news agency Tass from Accra, the Ghanaian capital, and sent out over its worldwide English-language service the same day. The Tass account was reprinted in the U.S. government-run Foreign Broadcast Information Service's Soviet Union Daily report Jan. 11.

The Tass account of the Ghanaian Times report said South Africa had sent its leading geneticist, Richard Ambrosio, to Fort Detrick Sept. 5, 1986, and described the laboratory as engaging in "the development of bacteriological weapons as well as gene engineering and its military application."

A South African Embassy official was unable to verify whether such a person exists but said similar allegations had been leveled against South Africa in Soviet-disseminated stories in the African press.

The Tass account said U.S. chemical-warfare specialists had become "frequent guests" in South Africa and were working with South Africans on developing 155mm chemical binary shells.

"The {Ghanaian} newspaper emphasizes that the greatest danger to Africa is posed by U.S.-South African experiments with ethnic weapons which possess selectivity in killing only people with dark-color skin," Tass wrote.