Sergei Losev, 61, general director of the Soviet Union’s official news agency Tass. In an announcement Tass said Losev, who had headed the agency since 1979, was a “man of great spiritual generosity” who “devoted all of his energy and experience to the work given him by the party and government.” Losev joined Tass in 1950 after graduating from the Moscow Institute of International Relations, and worked as a correspondent and bureau chief in the United States and Israel. He recently published a book on the Watergate affair and the resignation of President Richard M. Nixon. In 1973, he became assistant director of Tass. Losev was a member of the Communist Party’s Central Auditing Commission, a delegate to the last two Communist Party congresses and the June party conference. He had been a member of the Supreme Soviet as well. In Moscow on Monday of a heart attack.