NATO members in Portugal in 2010 agreed to withdraw combat forces from Afghanistan by 2014 as international forces focused on training national troops. Some alliance members have expressed reservations about the timetable given the rise of attacks by Afghan soldiers on international forces.
Pentagon spokesman George Little said that, while insider attacks were problematic, gains have been made elsewhere in the country.
"The transition process, which began a few years ago, is proceeding the way we expected it to," he said.
NATO Secretary-General Anders Fogh Rasmussen, elected Wednesday for another term, told The Guardian newspaper in London that the transition strategy in Afghanistan was fluid.
"Our troops can redeploy, take on other tasks, or even withdraw, or we can reduce the number of foreign troops," he was quoted as saying.
Little said suggestions that Rasmussen was looking for an exit was a misrepresentation of his comments.
"My understanding (is) that the secretary-general is, in fact, committed to the timeline that we're all working toward and that there is absolutely no daylight between us and the secretary general on the Lisbon strategy," Little said.