WASHINGTON (REUTERS) - Defence Secretary Chuck Hagel called sexual assault a "scourge" on Saturday as he addressed graduates of the US Military Academy at West Point, where a sergeant stands accused of videotaping female cadets in the showers.

"Sexual harassment and sexual assault in the military are a profound betrayal - a profound betrayal - of sacred oaths and sacred trusts," Mr Hagel said. "This scourge must be stamped out."

His comments came a day after President Barack Obama delivered a similar message to graduates at the US Naval Academy, saying sexual assault threatened to erode trust and discipline in America's armed forces. The Pentagon is reeling from a series of sex-related scandals in recent weeks, including cases in which military advocates for victims of sexual assault were themselves accused of sex crimes.

A study released by the Defence Department two weeks ago estimated that reports of unwanted sexual contact in the military, from groping to rape, rose 37 per cent last year to about 26,000 cases from 19,000 the previous year.

At West Point in New York state, Sergeant First Class Michael McClendon was charged last week with four counts, including indecent acts, dereliction of duty and cruelty, the Army said.

McClendon had served as a tactical non-commissioned officer at the academy since 2009, a job that put him in charge of mentoring and training a company of about 121 cadets.

The incidents have embarrassed the US military and prompted members of Congress to introduce legislation designed to toughen up the Pentagon's handling of sex crimes.

Mr Hagel, in his address, noted that budget cuts were impacting military readiness and morale, but he cited sexual assault and sexual harassment among other, growing threats to America's all-volunteer force.

"You will need to not just deal with these debilitating, insidious and destructive forces but rather you must be the generation of leaders that stop it," he said.