"(The post-2014 force) that decision I know has not been made yet. It's still under consideration. I have made my recommendation. That recommendation is for 13,600 US forces," Mattis said.
He was speaking at the members of the powerful Senate Armed Services Committee during a Congressional hearing.
He said no decision has been made on the number of Nato troops in Afghanistan after 2014, but his expectation is that would be 50% of the US forces.
Testifying before the Congressional committee, Mattis said the Afghan campaign is on track.