"Whoops," said one high-ranking administration official.
"Report reveals Vietnam War hoaxes, faked attacks"
On several occasions "the communists were able, by communicating on Allied radio nets, to call in Allied artillery or air strikes on American units," it said.
"That's something I have never heard before," Steven Aftergood, director of the FAS project on government secrecy, told AFP.
But he said that probably the "most historically significant feature" of the declassified report was the retelling of the 1964 Gulf of Tonkin incident.
That was a reported North Vietnamese attack on American destroyers that helped lead to president Lyndon Johnson's sharp escalation of American forces in Vietnam.
The author of the report "demonstrates that not only is it not true, as (then US) secretary of defense Robert McNamara told Congress, that the evidence of an attack was 'unimpeachable,' but that to the contrary, a review of the classified signals intelligence proves that 'no attack happened that night,'" FAS said in a statement.
"Yeah, it seems that the cat is out of the bag on this one," said the official. "I think if you look at the results some four decades later, though, you see it was a good thing."
The newly released report has helped direct a light into U.S. government strategies and plans, and whether they have been untruthful to U.S. citizens in the past.
"That's just ludicrous," said the official. "The times we are living in now are 1,000 times more perilous than during the days when all we had to worry about was communists. Since then, it's all been on the up and up. Really."