WASHINGTON, May 7 (JTA) — Charges that a top U.S. official passed highly sensitive information to Israel may open new fissures in relations between Washington and Jerusalem. The FBI opened an investigation in January after the National Security Agency intercepted a secure conversation between a Washington-based senior Israeli intelligence official and a superior in Israel, the Washington Post reported Wednesday. State Department officials confirmed the contents of the report. Israeli officials emphatically denied the charges. Israeli Prime Minister Benjamin Netanyahu called the story “absolutely baseless.” According to the Washington Post, the Israeli officials reportedly argued over whether to ask someone with the code-name “Mega” to obtain a secret letter that then-U.S. Secretary of State Warren Christopher had sent to Palestinian Authority leader Yasser Arafat as part of the Hebron agreement between Israel and the Palestinians. The Hebron deal, clinched in January by Israeli Prime Minister Benjamin Netanyahu and Arafat, required that Israel transfer most of the West Bank city to Palestinian rule, as well as a commitment to further West Bank withdrawals in the future. After the accord was signed, Christopher gave separate “side letters” to both sides, which were meant as assurances for both Israel and the Palestinians of the U.S. position, particularly with regard to future withdrawals. Israel immediately made public its letter, but the Palestinians never did. Based on the intercepted conversation, the FBI and the National Security Agency believe that “Mega” is a senior U.S. official who has passed information in the past. The Post reported that the Israeli intelligence official in Washington told his superior that Israel’s ambassador to the United States, Eliahu Ben Elissar had asked for a copy of the letter, according to the intercepted conversation which was translated from Hebrew. Citing a source who saw the transcript, the Post reported that the intelligence officer said, “The ambassador wants me to go to Mega to get a copy of this letter.” The Tel Aviv-based Mossad supervisor replied, “This is not something we use Mega for,” the Post reported. Ben Elissar emphatically denied to the Post that he had requested a copy of the letter to Arafat or that a U.S. government official was passing information to Israel.