Even at the top levels of the Johnson administration, where one
  might expect a consensus on the basic facts, we find opposing opinions
  on the fundamental question of whether the attack was accidental or
  deliberate. Lyndon Johnson in his memoirs called the attack "a tragic
  accident." Robert McNamara, his Secretary of Defense, has stated "I
  didn't believe [the attack] was intended at the time, and I don't
  believe it now." Dean Rusk, Johnson's Secretary of State (in the only
  instance where he disagreed with the President) wrote:

  "We also lost 34 American lives when, on June 8, the fourth day of 
  the war, the U.S. communications ship Liberty came under air and 
  naval attack.  We were meeting with President Johnson in the White
  House situation room, considering the implications had the Soviets or
  Egyptians attacked the ship, when we received word from Tel Aviv that
  Israeli forces were responsible.  That didn't please us, although an 
  Israeli attack on Liberty was far easier to deal with.  But I was never 
  satisfied with the Israeli explanation. Their sustained attack to
  disable and sink Liberty precluded an assault by accident or some
  trigger-happy local commander. Through diplomatic channels we 
  refused to accept their explanations.  I didn't believe them then, and 
  I don't believe them to this day. The attack was outrageous."

                       Rusk's memoirs:  "As I Saw It"  (W.W.Norton, 1990) p388