In his first major military move, President Barack Obama approved the deployment of 17,000 more troops to Afghanistan, saying they were needed "to stabilize a deteriorating situation."

"There is no more solemn duty as president than the decision to deploy our armed forces into harm''s way," Obama said in a statement.

"I do it today mindful that the situation in Afghanistan and Pakistan demands urgent attention and swift action."

Obama said the deployment orders were in response to a months-old request by the US commander in Afghanistan, General David McKiernan, who had asked for 30,000 more troops.

"To meet urgent security needs," Obama said he had approved a request by Defense Secretary Robert Gates to deploy a Marine Expeditionary Brigade in the spring, and an Army Stryker Brigade and support forces later this summer.

The White House said some 17,000 troops will be deployed to Afghanistan ahead of the Afghan elections scheduled for August 20, significantly building up the 38,000 US force already on the ground battling a growing insurgency.

Asked about possible future troop deployment orders, a senior administration official told AFP they were unlikely to come before an ongoing comprehensive review of US strategy in Afghanistan and Pakistan was completed.

"The thinking is that this was necessary at this time because of the expected increase of fighting in the spring and the upcoming elections," the official said on condition of anonymity.