(Washington, DC) -- President Obama is defending his Afghanistan policy amid criticism in a new book by former Defense Secretary Robert Gates. In remarks at the White House, the President called Gates an "outstanding" defense chief. Obama said finalizing a withdrawal strategy from Afghanistan was a difficult task conducted after months of intense analysis. NATO and U.S. combat troops are set to be out of Afghanistan by the end of next year. The President said he has confidence in the mission and troops. He warned that, while the war is winding down, troops remain in harm's way as the "job is not yet done."