WASHINGTON (AP) - The top US defense leaders were summoned to the White House on Thursday to talk about the military's sexual assault crisis as the Pentagon's top general said women in uniform were losing confidence the problem will be solved.

President Barack Obama planned to meet on Thursday afternoon with Defense Secretary Chuck Hagel, top-ranking officers and civilian leaders of all the service branches to discuss the issue, an administration official said on Thursday.

The official was not authorised to discuss the meeting publicly because it had not been announced and spoke on condition of anonymity.

Allegations of sexual assault in the military have triggered outrage from local commanders to Congress and the White House. Yet there seem to be few clear solutions beyond improved training and possible adjustments in how the military prosecutes such crimes.

Changing the culture of a male-dominated, change-resistant military that for years has tolerated sexism and sexist behavior is proving to be a challenging task.

"We're losing the confidence of the women who serve that we can solve this problem," the chairman of the Joint Chiefs of Staff, Army General Martin Dempsey, said on Wednesday.

"That's a crisis," Gen Dempsey said in remarks during a flight from Europe to Washington that were reported by the Pentagon's internal news service.

He suggested that a deepening of the sexual assault problem may be linked to the strains of war.

The Pentagon scheduled a briefing for journalists on Thursday with Mr Hagel and Gen Dempsey.

As new sexual assault allegations emerged this week involving an army soldier who was assigned to prevent such crimes - the second military member facing similar accusations - the Pentagon said Mr Hagel is working on a written directive to spell out steps aimed at resolving the escalating problem.

But President Barack Obama, fuming at a news conference last week, warned that he wanted swift and sure action, not "just more speeches or awareness programmes or training".

Sexual offenders need to be "prosecuted, stripped of their position, court-martialled, fired, dishonorably discharged. Period," he said.

Pentagon press secretary George Little added that Mr Hagel told Mr Obama on Tuesday about an Army sergeant first class at Fort Hood, Texas, who faces allegations of sexual misconduct. The case involves the soldier's activities with three women, including an allegation that he may have arranged for one of them to have sex for money, according to a defense official.

Those allegations follow a Pentagon report last week that estimated that as many as 26,000 military members may have been sexually assaulted last year, based on survey results, out of 1.4 million in the services.

That report, and a recent series of arrests and other sexual assault problems across the military, have triggered a rush of initiatives from the Pentagon and proposed legislation in Congress.

According to Mr Little, Mr Hagel is considering changes to the Uniform Code of Military Justice that would prevent commanders from reversing sexual assault convictions, along with other efforts to improve training, assist victims and strengthen discipline.

Mr Hagel has also ordered the retraining, recertifying and rescreening of all sexual assault prevention and response personnel as well as military recruiters, who also have been accused in recent sexual misconduct cases.

Democratic Senator Kirsten Gillibrand planned to introduce legislation on Thursday taking top commanders out of the process of deciding whether a sexual misconduct case goes to trial. For sexual offenses with authorised sentences of more than one year in confinement - akin to felonies in the civilian judicial system - that decision would rest instead with officers at ranks as low as colonel who are seasoned trial counsels with prosecutorial experience.

Just last week, an Air Force officer who headed a sexual assault prevention office was himself arrested on charges of groping a woman in a Northern Virginia parking lot.

In the recent Pentagon report, officials said that of the estimated 26,000 military members who may have been sexually assaulted last year, fewer than 3,400 reported the incidents. Nearly 800 of those simply sought help and declined to file formal complaints against their alleged attackers.