A roadside bomb attack killed four US soldiers in Afghanistan as pressure mounted Friday for President Barack Obama to order thousands more soldiers into an escalating eight-year war.
"Two US service members were killed and two died of wounds sustained in a single improvised explosive device attack in southern Afghanistan October 15," the NATO-led International Security Assistance Force (ISAF) said.
No further details were immediately available but thousands of US troops are fighting in southern Afghanistan as part of a push to quell a resurgent Taliban in what is their spiritual heartland.
The latest military deaths come as Obama debates whether to send thousands of additional troops to the impoverished country on top of 21,000 extra forces he committed after taking office this year.
In a grim assessment of a war with military casualties at record levels, the commander of the 100,000 US and NATO troops in Afghanistan, General Stanley McChrystal, has asked Obama for a reported 40,000 extra troops.
ISAF's commander in southern Afghanistan, Dutch Major General Mart de Kruif, told AFP in an interview Thursday that he wanted 10,000 to 15,000 more troops, including support units, to ensure security in the region.
He also called for more Afghan army and police plus civilian workers to help development and reconstruction projects.
Improvised explosive devices (IEDs) -- homemade, cheap and difficult to detect -- have become the Taliban's weapon of choice against foreign troops, as they look to regain influence across the country.
An AFP toll based on a tally by the independent website icasualties.org puts foreign military fatalities this year at 414 -- the bloodiest since US-led operations to oust the Taliban regime began in late 2001.
The US president is expected to unveil a new strategy within weeks to contain an insurgency fuelled by Al-Qaeda militants and the Taliban, which is resurgent eight years after US-led troops ousted them from power.
Obama has said the top goal of any new policy would be consistent with current US aims -- rooting out Al-Qaeda and its "extremist allies".
Compounding the military difficulties is speculation that Afghan President Hamid Karzai could be forced into a run-off without securing an outright majority at elections in August scarred by fraud allegations.
A fraud probe has trimmed Karzai's vote share to just 47 percent, The Washington Post said Friday.
The Independent Election Commission gave Karzai 54.6 percent in its preliminary results, which would secure him for a second five-year term.
But Afghanistan's ambassador to the United States, Said Tayeb Jawad, conceded for the first time that the disputed elections put Karzai and former foreign minister Abdullah Abdullah into a run-off.
On the ground, ISAF said two civilians lost their lives during a joint operation with Afghan police that killed a number of militants suspected of mounting attacks in eastern Ghazni province.
"During the operation, as militants attacked the joint force, a woman and school-aged girl were accidently killed in the crossfire," the statement said.
It added: "It is unclear if the enemy militants or the joint force are responsible for the deaths."
ISAF spokesman Colonel Wayne Shanks said they were "genuinely sorry" when Afghan civilians were killed but took steps to prevent civilian casualties.
Separate operations in southern Paktika province and Wardak, in the west, saw a number of suspected militants killed or detained, ISAF added.