WASHINGTON (AFP) - The US military vowed on Wednesday to address a wave of sexual assault cases after a soldier who worked in a rape prevention programme was accused of forcing a subordinate into prostitution.

The latest revelation marked the second time in a week that a member of the military assigned to work in its sexual assault prevention programme had been placed under investigation for alleged sexual crimes.

Following the new allegation, Defence Secretary Chuck Hagel ordered those working as recruiters and in sex assault prevention efforts to undergo fresh screening and training, his spokesman George Little told reporters.

"There is frustration on the part of this secretary," Mr Little said. "It's not just about talking about this issue. We have to take action and we have to take action swiftly." The Pentagon revealed on Tuesday that a US Army sergeant based at Fort Hood in Texas faces allegations of sexual assault, abusive sexual contact, mistreatment of subordinates and pandering - the legal term for pimping.

The sergeant, who was not named, was working as a "sexual harassment or assault response and prevention programme coordinator" at the huge base and has since been suspended from his duties.

Last week, an Air Force officer in charge of his service's sexual assault prevention office was arrested near the Pentagon for allegedly assaulting a woman in a parking lot, grabbing her breasts and buttocks.

According to Mr Little, Mr Hagel discussed the sexual assault problem in his weekly meeting with President Barack Obama on Tuesday.

Both agreed that urgent steps were needed and that anyone guilty of sexual assault had to be held accountable, he said, adding: "The president has made very clear his expectations on this issue."

The embarrassing allegations have put the Pentagon under growing pressure and provided ammunition to lawmakers and activists, who are pushing for major changes to military procedures to stem the problem.

There are growing calls in Congress to change the military's legal code, which allows commanders to weigh in on criminal cases and even to overturn verdicts or sentences.

Mr Hagel has proposed stripping commanders of the authority to toss out a verdict after a trial but had initially opposed more sweeping changes, which could remove sexual assault cases from the chain of command.

Mr Little said the Pentagon chief is now ready to consider "all options." Democratic Senator Kirsten Gillibrand, chair of the Senate Armed Services Subcommittee on Personnel, has blasted the Pentagon over the issue and demanded an overhaul of its justice system.

"It is time to get serious and get to work reforming the military justice system that clearly isn't working," the New York lawmaker said in a statement Tuesday.

"I believe strongly that to create the kind of real reform that will make a difference we must remove the chain of command from the decision making process for these types of serious offenses."

Senior military officers have been accused of failing to recognise the gravity of the problem and the US Air Force's chief, General Mark Welsh, came under heavy criticism over his remarks at a hearing last week.

Mr Welsh told lawmakers sexual assaults in the ranks reflected a wider societal problem, saying troops were influenced by a "hookup" culture among young people.

But the Pentagon distanced itself from his comments.

"It really doesn't matter if our (sexual assault) rates are similar to that of the rest of society, quite frankly," Mr Little said when asked about the remarks.

"We must hold ourselves to a higher standard, and that's what the American people demand."