The former US Navy SEAL who penned a book on the raid that killed Osama bin Laden revealed classified information in his first-hand account and could face criminal charges, officials said.
The Pentagon's warning came on Tuesday as the head of United States Naval Special Warfare Command, Rear Admiral Sean Pybus, voiced outrage that some current or retired commandos were trying to cash in on their fame.
"I am disappointed, embarrassed and concerned," Pybus wrote in a letter to troops, denouncing some former SEALs for delving into partisan politics or "hawking details about a mission against Enemy Number 1."
The US Defence Department has already threatened legal action over No Easy Day, which was released on Tuesday, but officials previously had stopped short of saying whether the book had revealed state secrets.
"We believe that sensitive and classified information is contained in the book," Pentagon spokesman George Little told reporters in the first such assertion.
Asked if the US government would take legal action against the author, Little said officials were reviewing all options.
"Legal avenues are available to us. I'm simply not going to get into what we may or may not decide," he said.
But he repeated the Pentagon's view that the author violated non-disclosure agreements that required him to submit his first person account - the first such eyewitness account of the bin Laden raid - for review by the military before publication.
Sending in the book for review was a simple matter of "common sense" and "a no-brainer" for anyone working in matters of national security, Little said.
"It is the height of irresponsibility not to have this kind of material checked for the possible disclosure of classified information. And we have very serious concerns after having reviewed the book."
The former Navy commando wrote No Easy Day under a pseudonym, Mark Owen, but was soon identified in media reports as Matt Bissonnette.
Last week, Bissonnette's lawyer offered a rebuttal to the Pentagon, insisting he had not broken faith with his commitments and that the non-disclosure agreements did not apply to the bin Laden operation.
Bissonnette said he went to great lengths to avoid uncovering sensitive details about tactics or technology, saying he had consulted a former special operations forces lawyer to review the manuscript. "If you are looking for secrets, this is not your book," he wrote.