President Donald Trump is reportedly preparing to pardon several US service members accused of war crimes before they stand trial.

Retired US Navy Adm. William McRaven, a former Navy SEAL who oversaw the Osama bin Laden raid in 2011, said on Tuesday that Trump "needs to be very careful" about presidential pardons.

McRaven said that any indication that Trump would pardon the service members could be considered undue influence.

McRaven is not alone. Retired US Marine Corps Gen. Charles Krulak said that if Trump moves forward with the pardons, "he will betray these ideals and undermine decades of precedent in American military justice that has contributed to making our country's fighting forces the envy of the world."

Democratic Rep. Jason Crow of Colorado, a retired US Army Ranger and combat veteran, told INSIDER that the possibility was "very troubling."

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Retired US Navy Adm. William McRaven, a former Navy SEAL who oversaw the Osama bin Laden raid in 2011, said President Donald Trump "needs to be very careful" about presidential pardons for US service members accused of war crimes.

"I think the president needs to be very careful at this point," McRaven told the Fox News host Bret Baier in an interview on Tuesday. "Obviously the president can pardon whoever he thinks it's appropriate to pardon. But as you know, Bret, the way it works in the military is you have to be careful as a senior commander about unduly influencing the process before the investigation has been adjudicated."

Trump is considering pardoning several service members and military contractors around Memorial Day, The New York Times reported on Saturday, citing two US officials.

The White House is believed to have requested dossiers on some high-profile cases, including that of Special Operations Chief Edward Gallagher, a Navy SEAL scheduled to appear in court next week on charges of killing an enemy prisoner and shooting Iraqi civilians in 2017, The Times said.

Read more: Trump reportedly wants to pardon accused or convicted war criminals in time for Memorial Day

While the pardoning process typically takes months, the Justice Department was asked to have the files ready by Memorial Day weekend, a senior military official told The Times.

Questions about Trump's willingness to pardon the men intensified after he pardoned former Lt. Michael Behenna, a US Army Ranger convicted of killing an Iraqi prisoner in 2008, earlier this month. The White House said in a statement that Behenna was a "model prisoner" during his incarceration and highlighted the military's "broad support" of his service.

Marine Gen. James Mattis and McRaven on Capitol Hill in March 2013. Evan Vucci/AP

McRaven, who last year rebuked Trump after the president sought to revoke the security clearances of former US intelligence officials, said on Tuesday that any pardons from the commander in chief ought to be delayed until the criminal matters are settled in court.

"A senior officer is not allowed to imply how he thinks the investigation should come out," McRaven said. "That is called unduly influencing the investigation. So by the president signaling that he wants to or might pardon any individual, I'm concerned that that unduly influences the commanders below him.

"Now, once the trial is over and the president has an opportunity to read all the evidence and make a decision, obviously he's well within his rights to pardon whoever he thinks it's appropriate to do so."

McRaven is not alone in this thinking. Retired US Marine Corps Gen. Charles Krulak, the 31st commandant of the Marine Corps, said in a statement on Tuesday that if Trump proceeds with the pardons, "he will betray these ideals and undermine decades of precedent in American military justice that has contributed to making our country's fighting forces the envy of the world."

Krulak told Task & Purpose: "We can talk all we want about what he's doing with the rule of law under his authority, but to start saying that a trial by jury under the [Uniform Code of Military Justice] is now something that can be overturned is sending just a terrible signal to the men and women who are currently serving."

He added that "it sets a precedent that we could possibly regret."

Democratic Rep. Jason Crow of Colorado, a retired US Army Ranger and combat veteran, described the possibility as "very troubling."

"The idea that the commander in chief, in this case President Trump, will interject before these cases are even heard or adjudicated is pretty astounding," Crow told INSIDER. "It undermines the good order in the ranks."