"the CIA assessed that Nasser’s military presence in the Sinai was defensive, stating that “Armored striking forces could breach the UAR’s double defense line in the Sinai in three to four days and drive the Egyptians west of the Suez Canal in seven to nine days. Israel could contain any attacks by Syria or Jordan during this period”
Neither U.S. nor Israeli intelligence assessed that there was any kind of serious threat of an Egyptian attack. On the contrary, both considered the possibility that Nasser might strike first as being extremely slim.
The current Israeli Ambassador to the U.S., Michael B. Oren, acknowledged in his book “Six Days of War“, widely regarded as the definitive account of the war, that “By all reports Israel received from the Americans, and according to its own intelligence, Nasser had no interest in bloodshed”.
Four days before Israel’s attack on Egypt, Helms met with a senior Israeli official who expressed Israel’s intent to go to war, and that the only reason it hadn’t already struck was because of efforts by the Johnson administration to restrain both sides to prevent a violent conflict.
“Helms interpreted the remarks as suggesting that Israel would attack very soon”, writes Robarge. He reported to Johnson “that Israel probably would start a war within a few days.”
Israel's attack on Egypt in June '67 was not 'preemptive' | Foreign Policy Journal
Arab-Israeli War of 1967
Arab-Israeli War of 1967
On the morning of June 5, 1967, Israel launched a preemptive strike against Egyptian forces in response to Egypt's closing of the Straits of Tiran. By June 11, the conflict had come to include Jordan and Syria. As a result of this conflict, Israel gained control over the Sinai peninsula, the Golan Heights, the West Bank, the Gaza Strip and East Jerusalem. Israeli claims on these territories, and the question of the Palestinians stranded there, posed a long term challenge to Middle East diplomacy.