WASHINGTON (Reuters) - President Barack Obama said on Wednesday he did not anticipate any "sudden" change in U.S. plans for the speed of withdrawing troops from Afghanistan, which some have demanded after the weekend killings of Afghan civilians by a U.S. soldier.
"In terms of pace, I don't anticipate at this stage that we're going to be making any sudden additional changes to the plan that we currently have," he told a joint press conference with British Prime Minister David Cameron.
Calling the shooting of 16 Afghans "tragic", Obama said the killings were a reminder of the challenging nature of the mission in Afghanistan, but emphasized that both nations remained committed to completing it "responsibly".
"There will be a robust coalition presence inside of Afghanistan during this fighting season to make sure that the Taliban understand that they're not going to be able to regain momentum," Obama said in the White House Rose Garden.
NATO leaders gathering in Obama's home city of Chicago on May 20-21 will decide the "next phase" of the planned transition to Afghan forces taking the lead for security in 2014, he said.
The two nations have the largest contingents of foreign troops in Afghanistan, but domestic support for the more than 10-year old war has flagged, posing a challenge to Obama as he campaigns for reelection on November 6.
The president acknowledged that people want the war over, but argued they still back the reason the United States invaded in the aftermath of the September 11, 2001 attacks on U.S. cities, plotted by al Qaeda militants from the sanctuary of Afghanistan.
"I think the vast majority of the American people and British understand why we went there," he said.
Forty percent of Americans said the shooting spree, in which nine children and three women were among those killed, had weakened their support for the war, according to an online poll by Reuters/Ipsos.
U.S. Defense Secretary Leon Panetta told troops in Afghanistan on Wednesday that the massacre should not deter them from their mission to secure the country ahead of the 2014 NATO withdrawal deadline.
Reporting By Jeff Mason, Matt Spetalnick and Alister Bull; Editing by Anthony Boadle