WASHINGTON: US President Barack Obama indicated on Tuesday the possibility of stepping up the pace of withdrawal from Afghanistan but said he had no plans to rush out of the war-ravaged country.

"I think it's important for us just to make sure that we are not ... in Afghanistan longer than we need to be," Mr Obama said in an interview with KCNC television.

But in another interview, Mr Obama stressed that it was also "important for us to make sure that we get out in responsible way, so that we don't end up having to go back in".

The United States, he said, did not want to leave Afghanistan "in a way that is just a rush for the exits".

A shooting rampage by a US soldier who has been accused of killing 16 Afghan civilians, including nine children, has increased calls in the US for expediting a planned withdrawal of its troops from Afghanistan. The Obama administration is already working on a plan to bring back all combat troops in three years and is negotiating a strategic agreement with Kabul which will allow it to have a role after the pullout as well.

US experts, appearing in various TV talk shows, however, warned that the Afghan security forces might not be ready in two years to shoulder security responsibilities. They also noted that the Karzai regime in Afghanistan was seen as corrupt and inefficient. These factors, the experts argued, could force the US to stay longer than it desired.

Mr Obama, who also consulted British Prime Minister David Cameron on Tuesday about "the way forward in Afghanistan", promised justice for the victims of the shooting spree. He said his administration would "spare no effort" in conducting a full investigation and following the facts "wherever they lead us".

Talking to reporters at the White House Rose Garden, Mr Obama reminded Americans that his main goal was dealing with Al Qaeda, which orchestrated the Sept 11, 2001 terrorist attacks in the United States.

"We will continue the work of devastating Al Qaeda leadership," he said. "I am confident that we can continue the work of meeting our objectives, responsibly bringing this war to a close."

The US media noted that Mr Obama used the word "responsibly" three times in his statements, to avoid giving the impression that the United States was planning an immediate pullout.

The US takes the killing of Afghan civilians by a deranged gunman "as seriously as if it were our own citizens and our own children who were murdered," Mr Obama said.

"It's not who we are as a country and it does not represent our military."

An ABC News-Washington Post poll released on Monday shows 60 per cent of Americans no longer think the war in Afghanistan is worth the costs. "From the public's perspective, the house of cards is falling and the US would do best to just pull out and cut their losses," the surveyors said.