Gorbachev Ally, 55, Replaces Ailing Soviet Premier, 80,

Associated Press

The Soviet Union announced today that Premier Nikolai A. Tikhonov has been replaced by Politburo member Nikolai I. Ryzhkov.

The official press agency Tass announced in a brief statement that Ryzhkov, 55, was appointed premier by a decree of the Supreme Soviet.

Tass said Tikhonov, 80, was relieved of his duties “for health reasons.” The agency said Tikhonov, in a letter to Soviet leader Mikhail S. Gorbachev, reported that his health had “considerably deteriorated lately” and that physicians had advised him to retire.

Tass said the letter was read by President Andrei A. Gromyko at a meeting of the presidium of the Supreme Soviet.

Tikhonov had been premier since 1980.

Ryzhkov, a Gorbachev ally, has been a member of the Politburo since April and is the party secretary on the Central Committee responsible for economic matters.