Halperin, who had signed with the Israeli team Maccabi Tel Aviv, played with Seattle during their summer league, much to the ire of the Israeli National Team, which was concerned about his level of fatigue.
The 22-year-old's agent -- an American -- was expected to arrive in Israel with his contract Monday.
Friends close to Halperin have said recently that no deal was certain, either with the Sonics or Maccabi.
Halperin has said in past interviews that he would prefer to wait for developments with the Sonics or other European teams before finalizing matters with Maccabi.
The Sonics chose Halperin with the 53rd pick in June's draft.