This book cover image released by Dutton shows "No Easy Day: The Firsthand Account of the Mission that Killed Osama Bin Laden," by Mark Owen with Kevin Maurer.

Washington - The Pentagon and a former US Navy SEAL are at odds over a book that offers the first eyewitness account of the May 2011 raid that took out Osama bin Laden, with a potential court battle looming.

Amid a wave of publicity, the Defence Department is warning the ex-commando and his publisher not to release No Easy Day next week, saying the author violated non-disclosure agreements he signed while in uniform.

The Pentagon said on Friday it has reviewed the text but officials declined to say if the book reveals state secrets, vowing to keep all legal options open.

“I'm not going to characterise one way or the other whether we think there's classified information in it,” press secretary George Little told reporters.

“We are going to preserve our options.”

The Pentagon's top lawyer on Thursday threatened possible legal action, saying the author had violated the non-disclosure deals - including a pledge to submit any book for review before publication.

“Those agreements are very clear, that when you write something that may contain classified information, you need to have it go through pre-publication review by this department,” Little said.

“That did not occur in this case.”

The former Navy commando wrote “No Easy Day” under a pseudonym, Mark Owen, but has been identified in media reports as Matt Bissonnette.

In the book, published by Penguin's Dutton imprint and already handed out to some US media, he describes his role in the famed raid on bin Laden's Pakistani hideout that was hailed afterward as a triumph by the White House.

With the book expected to hit instant best-seller status, Bissonnette's lawyer on Friday offered a rebuttal to the Pentagon, insisting the author had not broken faith with his commitments.

The commando had sought legal advice before going ahead with the book and was not required to submit the manuscript in advance to Defence officials as the Pentagon claims, said his attorney, Robert Luskin.

The former commando “is proud of his service and respectful of his obligations,” Luskin wrote to the Pentagon.

“But he has earned the right to tell his story; his abiding interest is to ensure that he is permitted to tell it while recognising the letter and spirit of the law and his contractual undertakings.”

The book does not offer a dramatically different version of events already presented by President Barack Obama's aides but does provide some new details about the May 2011 operation at bin Laden's compound in Abbottabad.

Bissonnette recounts how bin Laden was first shot in the head as he peered out of a door and then pumped with bullets as he convulsed on the floor.

Previous official accounts said bin Laden had appeared in a doorway and ducked back into his bedroom, leading the US commandos to suspect he might be retrieving a gun.

In some cases involving tell-all books, the US government has successfully sued intelligence officers for breaking their non-disclosure agreements, but it was unclear if federal authorities would take the same approach.

Judges have ruled current or retired employees have to secure approval of books before publication - regardless of whether classified information is disclosed.

The government then can demand access to any profits from the unauthorised books, said Steven Aftergood of the Federation of American Scientists, who writes a blog on government secrecy.

The non-disclosure agreements “have been consistently construed by courts as a binding contract,” Aftergood told AFP.

Failing to submit a manuscript qualifies as a civil case, but if the Pentagon concludes secrets were spilled in the book, the former commando could be subject to criminal prosecution.

Last year, a federal judge ruled in favour of the CIA in a case involving a former spy, saying the agent failed to obtain approval for his book, “The Human Factor,” before publication.

But with “No Easy Day,” experts say the author and publisher may be gambling that they have steered clear of exposing secrets and can argue their case on the non-disclosure agreements, all the while benefiting from the avalanche of publicity generated by the dispute.

“If the US government continues over a period of time to threaten prosecution, lawyers' fees will eat into his book royalties but, given that it is a pre-publication number one best seller, he will be able to bear that financial burden,” said Gary Solis, a retired Marine Corps lawyer and adjunct professor at Georgetown Law School.

“I believe Bissonnette ultimately will walk away with a tidy sum.”

Bissonnette reportedly plans to donate most of the proceeds to military charities. - Sapa-AFP