WASHINGTON (AP) -- Suicides in the US military surged to a record 349 last year, far exceeding American combat deaths in Afghanistan, and some private experts are predicting the dark trend will worsen this year.

The Pentagon has struggled to deal with the suicides, which Defence Secretary Leon Panetta and others have called an epidemic. The problem reflects severe strains on military personnel burdened with more than a decade of combat in Afghanistan and Iraq, complicated by anxiety over the prospect of being forced out of a shrinking force.

Pentagon figures obtained Monday by The Associated Press show that the 349 suicides among active-duty troops last year were up from 301 the year before and exceeded the Pentagon's own internal projection of 325. Statistics alone do not explain why troops take their own lives, and the Pentagon's military and civilian leaders have acknowledged that more needs to be done to understand the causes.

Last year's total is the highest since the Pentagon began closely tracking suicides in 2001. It exceeds the 295 Americans who died in Afghanistan last year, by the AP's count.

Military suicides began rising in 2006 and soared to a then-record 310 in 2009 before levelling off for two years. It came as a surprise to many that the numbers resumed an upward climb last year, given that US military involvement in Iraq is over and the Obama administration is taking steps to wind down the war in Afghanistan.

The Army, by far the largest of the military services, had the highest number of suicides among active-duty troops last year at 182, but the Marine Corps, whose suicide numbers had declined for two years, had the largest percentage increase - a 50 per cent jump to 48. The Marines' worst year was 2009's 52 suicides.

The Air Force recorded 59 suicides, up 16 per cent from the previous year, and the Navy had 60, up 15 per cent.

All of the numbers are tentative, pending the completion later this year of formal pathology reports on each case.