President Obama called the weekend killings of Afghan civilians unacceptable and outrageous and said anyone involved will be held accountable "with the full force of the law."
Speaking in the Rose Garden on Tuesday, Obama said he was "heartbroken over the loss of innocent life." An American soldier is accused of leaving his base in a remote part of southern Afghanistan on Sunday and shooting Afghan civilians. At least 16 died, including nine children.
"The United States takes this as seriously as if it were our own citizens and our own children who were murdered," he said.
The killings come in the wake of Afghan anger over U.S. soldiers unintentionally burning copies of the Koran, which led to several incidents of Afghan troops turning their weapons on their coalition allies.
The president said he has directed the Pentagon to spare no effort in conducting a full investigation. "I can assure the American people and the Afghan people that we will follow the facts wherever they lead us," he said. "And we will make sure that anybody who was involved is held fully accountable with the full force of the law."
The recent turmoil is heightening calls for speeding up the withdrawal of the more than 90,000 American troops still in Afghanistan. The New York Times reported on Tuesday that three options were being considered by the White House: one backed by Thomas Donilon, the national security adviser, to bring at least 10,000 more troops home by the end of December, and 10,000-20,000 more by June next year.
A second plan, preferred by Vice President Joe Biden, would do a bigger withdrawal, while the third - the military commanders' opinion - would maintain the troop level for as long as possible.
But Obama said the strategy to wind down U.S. involvement would continue as planned. "We are steadily transitioning to the Afghans who are moving into the lead," he said.