The secretive Navy SEALs are coming out of the shadows for a new Hollywood film, with elite commandos cast in starring roles in a radical departure for America's special forces.

In "Act of Valor," the select troops who call themselves "the quiet professionals" take a turn as leading men on the big screen, reciting lines from a script as they race to prevent terrorists from carrying out an attack on the United States.

Filming began in 2007, before the Navy's Sea, Air and Land Teams were catapulted to fame for their daring raid last May that killed Al-Qaeda mastermind Osama bin Laden.

US defense officials did not find out about the movie until after the fact, causing consternation at the Pentagon, which has an office that vets scripts and negotiates cooperation deals with Hollywood producers.

Although troops have appeared in movies before, such as "Black Hawk Down," this film ventures into uncharted territory, possibly jeopardizing the anonymity that the special forces have sought to safeguard.

"It's one thing to be filmed parachuting out of a plane, but it's another thing to be parachuting and land on the red carpet," a defense official, who spoke on condition of anonymity, told AFP.

Premiering on February 24, the action-packed movie tells the fictional story of SEALs rescuing a kidnapped CIA agent from a Central American drug cartel, only to uncover a terror plot against the United States by a Chechen jihadist.

The project started out as a vaguely defined recruiting movie with directors Mike "Mouse" McCoy and Scott Waugh filming the SEALs training exercises, but eventually evolved into a full-blown feature film.

The initial plan was to hire actors to play the special operations warriors, but McCoy's production company, the Bandito Brothers, managed to persuade active duty commandos to take the leading roles.

"It became an obsession to tell the story in an authentic way. We thought the only way to do it was with the real guys," McCoy says on the film's website.

There has been a decidedly "mixed reaction" to the movie project at the Pentagon, the defense official said.

"Obviously, clearly we wish it had gone through the normal channels," said Vince Ogilvie, deputy director for entertainment media at the Pentagon.

"But under the circumstances if they had come to us, we would probably have approved it pretty much the way it turned out anyway."

The officer who oversees the SEALs and other elite troops as head of Special Operations Command, Admiral William McRaven, has defended the movie as a valuable recruiting tool that reveals no classified tactics or techniques.

"We're conscious of the fact that they are active duty Navy SEALs in there. I can tell you they volunteered. There was no concern on their part of their individual (security) or the security of their family."

The names of the commandos in the film do not appear in the credits, and instead the movie lists naval special warfare troops killed since the attacks of September 11, 2001.

The full range of the SEALs' craft is on display in the film, including a high-altitude parachute jump, commandos rappelling from a helicopter and an underwater exit from a submarine.

The makers of "Act of Valor" promise realistic, jarring action, including footage of SEAL drills using live rounds.

But it's unclear if the commandos can convey the same authenticity when they deliver their dialogue.

"The hardest part was saying the lines. Running around and shooting guns and moving and communicating, thats commonplace. Thats nothing," said one of the commandos in the movie, identified as Ajay.

Trailers for the movie offer an appeal to patriotism ("Courage, Loyalty, Honor,") and a straight-ahead storyline based on a fight against terrorists, without delving into the unpopular wars in Iraq and Afghanistan.

Althought a script that avoids political minefields may not win any Oscars, it likely helped win the cooperation of the Navy commandos.

But the screen debut of active duty troops from a community that has always shunned media attention has irked some inside the military, who worry that a line has been crossed.

Defense officials at one point even weighed whether to prevent the film's release by withdrawing legal permission for footage of the SEALs and military hardware.

But the office that handles Hollywood requests reviewed the movie and concluded that it passed muster, officials said.

The Pentagon, however, does not want a repeat of the episode and is spreading the word to commanders that future movie projects -- including a possible film on the Bin Laden raid -- must be approved beforehand, the defense official said.

"This hasn't been swept under the carpet," he said.