WASHINGTON - US President Barack Obama said Tuesday that the US could still meet its objectives in Afghan war despite recent incidents including the shooting rampage by a US soldier which killed 16 Afghan civilians over the weekend.

"There's no question that we face a difficult challenge in Afghanistan, but I'm confident that we can continue the work of meeting our objectives, protecting our country and responsibly bringing this war to a close," the president said in a White House statement.

"Meanwhile, we will continue the work of devastating al-Qaeda's leadership," he added.

The weekend shooting spree, along with the violent protests by Afghans over the burning of Qurans by NATO troops last month, has put the Obama administration's Afghan strategy into question.

Republican presidential hopeful Newt Gingrich said shortly after the shooting rampage that the US involvement in the region around Afghanistan may be risking the lives of young troops in a mission that "may not be doable."

In the statement, Obama said he had directed the Pentagon to spare no efforts in a full investigation into the incident.

"I can assure the American people and the Afghan people that we will follow the facts wherever they lead us, and we will make sure that anybody who was involved is held fully accountable with the full force of the law," he said.

US Defense Secretary Leon Panetta said Monday that the American soldier who was accused of killing Afghan civilians including women and children could face death penalty if convicted.