US President Donald Trump is reportedly showing renewed interest in a proposal by Blackwater founder Erik Prince to privatize the US war in Afghanistan, amid Trump's growing frustration about the US military strategy in the war-torn country.

The idea envisions replacing troops with so-called private military contractors, or mercenaries, who would work for a special US envoy for the war who would report directly to the president, according to NBC News.

Prince's idea, which first surfaced last year during Trump’s Afghanistan strategy review, has raised ethical and security concerns among US military officials, key lawmakers in Congress and members of Trump's national security team.

NEW: Exclusive: President Trump is increasingly venting frustration about US strategy in Afghanistan, and showing renewed interest in a proposal by Blackwater founder Erik Prince to privatize the war, current and former sr. admin. officials tell @NBCNews. https://t.co/EuVQIDvAbk — MSNBC (@MSNBC) August 17, 2018

Trump’s advisers are worried his impatience with the Afghanistan conflict will cause him to seriously consider proposals like Prince's or abruptly order a complete US withdrawal, officials said.

In an interview with NBC News, Prince said he believes Trump advisers who oppose his plan are painting "as rosy a picture as they can" of the situation in Afghanistan.

"I know he's frustrated," Prince said of the president. "He gave the Pentagon what they wanted. ...And they haven't delivered."

As head of Blackwater, Erik Prince’s mercenaries committed multiple war crimes in Iraq and were convicted for their involvement in the Nissour Square massacre that killed 17 civilians. He deserves an investigation, not contracts to wage a private war in Afghanistan. https://t.co/fiWy1HYTIW — Rep. Ro Khanna (@RepRoKhanna) August 17, 2018

In August 2017, Trump went against his election campaign promise to pull American forces out of Afghanistan, announcing in a surprise move that Washington would drop a withdrawal timeline and commit even more troops to the country.

Most Americans have forgotten about the the US war in Afghanistan -- the longest war in US history -- or have no knowledge of the extent that the Pentagon still operates in the war-torn country, said Myles Hoenig, who ran for Congress in 2016 as a Green Party candidate.

“The idea that President Trump wants to privatize the war in Afghanistan is not entirely new. He wants a mercenary army answerable to a viceroy who would report directly to the emperor, the president,” Hoenig said Monday in an interview with Press TV.

“We saw something like this in Iraq, with Paul Bremer serving as the leading viceroy answerable to President George W. Bush. Many of the soldiers were mercenaries under the leadership of Erik Prince, the brother of Education Secretary Betsy DeVos,” he added.

“President Trump likes family affairs. His is a government that runs on nepotism and gangsterism. DeVos’s brother now having such strong influence is par for the course,” Hoenig said. “Having a mercenary army running operations in Afghanistan, with a viceroy answerable directly to Trump, also plays into Trump’s extreme narcissism and desires for a lifetime presidency, or emperor.”

The United States now has about 16,000 troops based in Afghanistan. It has also lost over 2,370 military servicemen in the course of the so-called war on terror, according to the latest figures.