Mattis on Afghan war: 'Privatizing it is probably not a wise idea' Mattis spoke to reporters in the Petagon's briefing room Tuesday.

Defense Secretary James Mattis pushed back on the idea of privatizing the war in Afghanistan on Tuesday, weeks after President Donald Trump's national security adviser appeared to leave the possibility open.

"When Americans put their nation's credibility on the line, privatizing it is probably not a wise idea," Mattis told reporters during a rare appearance in the Pentagon Briefing Room. Mattis was joined by Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford.

Earlier this month, John Bolton, the president's national security adviser, was asked whether private contractors could replace U.S. forces in Afghanistan. NBC News reported that Trump had shown interest in the idea, which had been proposed by Blackwater founder Erik Prince.

But in an interview with ABC News' Martha Raddatz Aug. 19, Bolton wouldn't say whether Trump was still considering it.

"There's always a lot of discussions," Bolton said. "I'm always open to new ideas, but I'm not going to comment on what the thinking is. That will ultimately be the president's decision."

Prince, who now heads Hong Kong-based security firm Frontier Services Group, is the brother of Trump's education secretary, Betsy Devos.

While Prince has advocated for the use of private contractors in Afghanistan before, his renewed efforts to gain traction for the proposal are tied to the one-year anniversary of the Trump administration's new strategy for America's longest war. In a press release following the NBC News report Aug. 20, Prince called the Pentagon's plan for Afghanistan "a total failure."

In the same press release, Prince outlined a plan involving a blend of private contractors and U.S. special forces who would mentor Afghan battalions in much the same way the U.S. is currently training, advising, and assisting Afghan troops now. Prince denied he was proposing a privatization of the war.

"What I am proposing will end the conflict, save the lives of hundreds of US armed forces personnel (and thousands of Afghans), and will cost only a fraction of what we currently spend. To emphasize, this is not a privatization of the war effort as has been wrongly stated by my critics. It is actually a reduction in the number of private contractors engaged in Afghanistan," Prince wrote in the statement.

Prince said in the same statement that the operation would be "fully accountable" under the Uniformed Code of Military Justice and the Afghan government's rules of engagement. He also estimates the need for only 6,000 contractors and 2,000 U.S. troops, compared to the approximately 14,000 Americans who are currently deployed.

There are more than 26,000 private contractors already serving in Afghanistan, according to the latest estimate from the offices of the inspector general at the Department of Defense, the State Department, and USAID.

On Tuesday, Mattis defended the president's new strategy for a war that is now entering its 17th year. Mattis pointed to the recent multi-day ceasefire between the Taliban and the Afghan government as a sign of progress, along with a new ceasefire offer from the government, which has not yet been accepted.

"We think there are positive reasons to stick with the strategy," Mattis said. "And we are going to drive this to a negotiated settlement -- [it] is our goal. That remains the same."

He said the Taliban's recent assault on the eastern city of Ghazni was not "emblematic" of the terrorist organization's strength, though it took Afghan and U.S. forces four days to end the siege. Afghan forces took 100 casualties in two days and nine Americans were evacuated from the battlefield with injuries during the operation to retake Ghazni earlier this month, according to a Time reporter who embedded with U.S. special forces there.

"I don't believe that you can use this example as emblematic because if you look at where the Taliban were and what they were claiming they were going to do two years ago, one year ago, they have not succeeded in taking down these towns and holding these towns," Mattis said.

"It's enormously easier to be the criminal in a town than it is to be the policeman. And that's true whether you're in Ghazni, Afghanistan or anywhere else," he added.

Speaking to reporters last week, the outgoing commander of U.S. forces in Afghanistan, Gen. John Nicholson, said that reconciliation efforts are gaining momentum despite the Taliban's high-profile and frequent attacks across the country this summer and no significant reduction in the amount of land the group controls.

Nicholson called the current moment "an unprecedented ... window of opportunity for peace" that did not exist under the Obama administration because "the enemy had no incentive to negotiate because we were leaving."

Trump and top U.S. military leaders have played up the fact that the new strategy is not based on timelines, but critics allege that such a plan leaves the door open for a long-term U.S. presence in the region similar to the one in Germany after World War II.

"What I would tell you there is that we have permanent interests in South Asia, diplomatic interests and security interests, and we're going to maintain a presence to have influence in that region," Dunford said on Tuesday when asked about a long-term U.S. presence in Afghanistan. "The diplomatic presence, the security presence, and the form of that presence is going to change over time."

"But I certainly don't expect that the current forces that we have in Afghanistan represent an enduring, large military commitment," Dunford added.

Mattis said any timeline for a troop withdrawal would be "situationally dependent" on Afghan forces' ability to successfully maintain the security of the country so that terrorist groups like the Taliban and ISIS don't have safe havens from where they can plan attacks.

"One of my concerns we always have-- and why this region remains so important -- is that there are 21 terrorist groups here, and we see members shift allegiances between the groups," Nicholson said last week when asked why the U.S. military was still in Afghanistan.

"So keeping pressure on the entire system is important in order to prevent the emergence of some new threat to the homeland," he continued. "So, our presence here does protect the homeland and prevents another Sept. 11. I firmly believe that."