Prime Minister Yitzhak Shamir has chosen former Soviet prisoner and human rights activist Natan Sharansky to be Israel's new ambassador to the United Nations, a senior government official said Tuesday.

News of the choice raised concern among some Israeli diplomats about the possibility of offending the Soviet Union at a time when relations with Moscow, broken off more than 20 years ago, are improving.A senior government official said Shamir's selection of Sharansky was expected to get the necessary approval from Finance Minister Shimon Peres, head of the left-leaning Labor Party. Labor shares power with Shamir's Likud bloc in the coalition government.

Sharansky, 41, served nine years of a 13-year sentence in Soviet prisons and labor camps on charges of spying. He was released Feb. 11, 1986, as part of an East-West prisoner exchange and flew immediately to Israel to join his wife, Avital.

He was arrested in 1977 after angering the Soviet authorities as an outspoken leader of the Jewish emigration movement and for maintaining numerous foreign contacts. Sharansky also belonged to a human rights watch committee headed by Andrei Sakharov that was sharply critical of Kremlin policies toward prisoners and national minorities.

The outspoken Sharansky, interviewed Tuesday on army radio, would not comment, saying only he had not been officially offered the job. Pressed by the interviewer, Sharansky added: "I will say only what I want to say. I have enough experience with interrogations and I know how to give answers. I have had no formal proposal."

Israel radio said Shamir's surprise choice of Sharansky followed a recommendation from former U.N. Ambassador Benjamin Netanyahu, now deputy foreign minister. Israel has not replaced Netanyahu since he left the post last year.