Defense Secretary Jim Mattis said Monday that all options for a new strategy in Afghanistan, including the use of private security contractors, remain under consideration by President Trump.

Mattis said he believes a decision is "very, very close" after months of deliberation and that the administration is continuing to hone various options being presented to the president.

The plans could lead to sending an addition 3,000-4,000 U.S. troops to Afghanistan, but the president reportedly has been frustrated by his options in the nearly 16-year-old conflict and has considered firing the U.S. commander in Afghanistan.

"We're sharpening each one of the options," Mattis said. "You can see the pluses and minuses of each one so that there's no longer any new data you are going to get. Now, just make the decision. There's the options."

As deliberations continue, the future is uncertain for Gen. John "Mick" Nicholson, who heads the NATO-led force in Afghanistan, which includes the U.S., according to Mattis.

"He is our commander in the field. He has the confidence of NATO. He has the confidence of Afghanistan. He has the confidence of the United States, and the president, again, is looking at all aspects of our effort over there, as he must in his responsibilities as commander in chief," he said.

Mattis confirmed that Trump is weighing a plan to privatize parts of the U.S. war effort there with up to 5,500 security contractors and a private air force of 90 aircraft. The proposal was suggested by Erik Prince, the founder of the Blackwater security firm and brother of Education Secretary Betsy DeVos.

"It's part of the options being considered and the president's open to the advice of the secretary of state and myself and the director of the CIA," Mattis said.