I'm not sure that this is true. James Ennes does state that an Israeli aircraft (an American-made F-100 Delta Dart was used, I believe) made low level surveilance passes over the Liberty hours (several hours, I believe) before the attack.
I do not blame Israel for attacking the Arab States (pre-emptive, or otherwise). I only want to know about what happened with the USS Liberty. It seems to me that if the Israelis really did suspect the Liberty of being Egyptian ship, a call to the US Navy could have helped avoid an "accident".
Ennes, I believe, also uncovered some evidence from US military sources of a similar incident that occured months earlier against a US ship where the Israelis warned the US against having inteligence-gathering ships poking around the area. No shots were fired on that occasion. If this is true, then it would bolster claims that the Israelis knew exactly who the USS Liberty was.
Will we ever know and can we ever trust "new" documments that surface, magically to support one side, or the other? I seriously doubt it.