Kennedy, however, was determined not to let Ben-Gurion change the subject. On May 4, 1963, he replied to the prime minister, assuring him that "we are watching closely current developments in the Arab world". As to Ben-Gurion's proposal for a joint superpower declaration, Kennedy dismissed both its practicality and its political wisdom. Kennedy was much less worried about an "early Arab attack" than he was by "a successful development of advanced offensive systems which, as you say, could not be dealt with by presently available means." Kennedy, would not budge on Dimona, and the disagreements became a "pain in the neck" for him, as Robert Komer later wrote. The confrontation with Israel escalated when the State Department transmitted Kennedy's latest letter to the Tel Aviv embassy on June 15 for immediate delivery to Ben-Gurion by Ambassador Barbour. In the letter Kennedy fleshed out his insistence on biannual visits with a set of detailed technical conditions. The letter was akin to an ultimatum: If the U.S. government could not obtain "reliable information" on the state of the Dimona project, Washington's "commitment to and support of Israel" could be "seriously jeopardized." But the letter was never presented to Ben-Gurion. The telegram with Kennedy's letter arrived in Tel Aviv on Saturday, June 15, the day before Ben-Gurion's announcement of his resignation, a decision that stunned his country and the world. Ben-Gurion never explained, in writing or orally, what led him to resign, beyond citing "personal reasons." It is widely believed that the Lavon Affair, a botched Israeli spy mission in Egypt, was the impetus for his resignation. He denied that his move was related to any specific policy issues, but the question of the extent to which Kennedy's Dimona pressure played a role remains open to discussion to the present day. On July 5, less than 10 days after Levi Eshkol succeeded Ben-Gurion as prime minister, Ambassador Barbour delivered to him a first letter from President Kennedy. The letter was virtually a copy of the undelivered letter of June 15 to Ben-Gurion. As Yuval Ne’eman stated, it was immediately apparent to Eshkol and his advisers that Kennedy's demands were akin to an ultimatum, and thus constituted a crisis in the making. A stunned Eshkol, in his first and interim response, on July 17, requested more time to study the subject and for consultations. The premier noted that while he hoped that U.S-Israeli friendship