President Trump has given Defense Secretary Jim Mattis the authority to decide the number of U.S. troops in Afghanistan.

Mattis will now be "the decider" on the matter and an official announcement is expected on Wednesday, a senior Pentagon official told the Washington Examiner. There are currently about 8,400 troops in Afghanistan.

Reuters broke the story hours after Mattis testified before the Senate Armed Services Committee and lamented U.S. progress in helping Afghan forces defeat the Taliban. "We're not winning in Afghanistan right now," he said.

The official told the Washington Examiner that while the number of troops Mattis might add to the fight is in the range of 3,000 to 5,000 soldiers, no decision has been made yet.

Asked about it on Air Force One on Tuesday, White House deputy press secretary Sarah Sanders wouldn't comment.

"I don't have anything I can comment on that right now. I would refer you to Secretary Mattis at this point," she told reporters according to a pool report.

In April, Trump handed authority over to the Pentagon to decide U.S. troops numbers in Iraq and Syria where a fight is being waged against the Islamic State.