WASHINGTON: In an unannounced move, President Barack Obama is dispatching an additional 13,000 US troops to Afghanistan beyond the 21,000 he announced publicly in March, The Washington Post reported.

The additional forces are primarily support forces -- such as engineers, medical personnel, intelligence experts and military police -- the Post said, bringing the total buildup Obama has approved for the war-torn nation to 34,000.

"Obama authorized the whole thing. The only thing you saw announced in a press release was the 21,000," a defense official familiar with the troop-approval process told the daily.

The report, posted on the newspaper's website late Monday, came as Obama weighs a request from the top US and NATO commander in Afghanistan, General Stanley McChrystal, for more combat, training and support troops, with several options including one for 40,000 more forces.

But the newspaper noted that the maximum number of US service members expected in Afghanistan by year's end -- 68,000 -- would remain the same.

Major deployments of support troops have not been publicized by the Pentagon and the White House in the past. When former presidentGeorge W. Bush announced a US troop increase in Iraq, he only mentioned 20,000 combat troops and not the accompanying 8,000 support troops.

The troop increase approved by Obama brought the level of US forces deployed in the Iraq and Afghanistan theaters to a total greater than during the peak of the surge in Iraq in late 2007 and early 2008.

At the start of this month, some 65,000 US forces are currently in Afghanistan and about 124,000 in Iraq, compared to around 26,000 US troops in Afghanistan and 160,000 in Iraq at the height of the Iraq surge, according to a troop count by the Post.