WASHINGTON (Reuters) - President Barack Obama, calling Afghanistan’s security situation precarious, said on Wednesday he will keep U.S. troop levels there at 8,400 through the end of his administration rather than reducing them to 5,500 by year’s end as previously planned. Obama, in a statement at the White House, said the role of U.S. forces in Afghanistan will remain unchanged: training and advising Afghan police and troops, and supporting counterterrorism missions against the Taliban and other groups. Obama’s presidency ends in January. Obama’s plan still calls for a reduction in U.S. troop levels from the current roughly 9,800, but not as much as previously planned. Obama, who took office in 2009 pledging to wind down the U.S. wars in Iraq and Afghanistan, said he had ended America’s combat mission in Afghanistan. But he acknowledged that security concerns persist. “The security situation in Afghanistan remains precarious,” Obama said. “The Taliban remains a threat. They’ve gained ground in some places.” Taliban forces now hold more territory in Afghanistan than at any time since the 2001 U.S.-led invasion, according to recent United Nations estimates. The Islamic State group has also established a small presence in Afghanistan. Obama’s decision, which came after a review submitted last month by the U.S. commander in Afghanistan, Army General John Nicholson, drew some criticism inside and outside his administration. Some Pentagon officials said that it does nothing to address the deteriorating security situation in Afghanistan. “It’s disappointing that the administration thinks that troop numbers are a substitute for a more comprehensive strategy,” said a U.S. defense official, who spoke on condition of anonymity. “This is neither the reduction that the White House seems to have wanted nor the current numbers that don’t seem to be sufficient to deal with the security problem.” Mac Thornberry, the Republican chairman of the House of Representatives Armed Services Committee, criticized what he said was a new cap on U.S. troop levels. “It is time that the president level with the American people about what it will really take to achieve our goals in Afghanistan, and how much it will cost,” Thornberry said in a statement.  Obama spoke in advance of a NATO summit on Friday and Saturday in Warsaw, Poland, where alliance members are expected to confirm their support for the Kabul government. In addition to the U.S. forces, there are about 3,000 other international troops in Afghanistan. U.S. troops have been in Afghanistan since the 2001 invasion launched by Obama’s predecessor, George W. Bush, that toppled the Taliban leaders who harbored the al Qaeda organization responsible for the Sept. 11 attacks on the United States that killed about 3,000 people. It is America’s longest war. During his announcement at the White House, Obama was flanked by Defense Secretary Ash Carter and the top U.S. military officer, General Joe Dunford, chairman of the Joint Chiefs of Staff. 