Pentagon chief Jim Mattis on Tuesday warned lawmakers that the Taliban is surging in Afghanistan, and said America is "not winning" in the country.

The "Taliban had a good year last year, they are trying to have a good one this year," Mattis told the Senate Armed Services Committee. "Right now I believe the enemy is surging."

He earlier told lawmakers: "We are not winning in Afghanistan right now. We will correct this as soon as possible."