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WASHINGTON — President Donald Trump said Tuesday that he stood behind Dr. Ronny Jackson, his nominee to be Veterans Affairs secretary, who is facing allegations of drinking on the job, overprescribing drugs and creating an unprofessional work environment.

But Trump added, "If I were him ... I wouldn't do it."

The confirmation hearing for Jackson, the White House physician who shared the results of Trump's annual physical with the press earlier this year, was scheduled for Wednesday, but was postponed amid concerns over the allegations of inappropriate behavior.

Sen. Jon Tester, D-Mont., the ranking member of the Veterans Affairs Committee, said on NPR on Tuesday that the allegations included "improper dispensing of prescription drugs, repeatedly drunk while on duty while traveling, and creating a toxic work environment."

Tester said most of the prescription drugs "are the ones that make you want to sleep, and make you wake up." He said the information was provided to him by "20 military folks and retired military folks."

"These were doled out on overseas trips where there's a lot of time-zone changes, and were pretty much doled out as somebody wants to go to sleep, here's a pill," he said, noting that there was no allegations of opioid abuse.

Regarding the allegations of Jackson's drinking on the job, Tester said, "It was on travel, and he is the physician for the president and in the previous administration we were told stories where he was repeatedly drunk while on duty where his main job was to take care of the most powerful man in the world. That's not acceptable."

The White House on Tuesday night strongly defended Jackson.

"Dr. Jackson's record as a White House physician is impeccable," a senior White House official said. "He has improved unit morale, received glowing reviews and promotions under Republican and Democrat presidents, and has been given a clean vet from the FBI."

A 2012 watchdog report ordered up by Jackson found that both he and a rival physician, Dr. Jeffrey Kuhlman, exhibited "unprofessional behaviors" as they engaged in a power struggle over the White House medical unit, according to The Associated Press, which reviewed the six-page report.

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The report suggested that the White House consider replacing Jackson or Kuhlman, or both. Kuhlman was the physician to President Barack Obama at the time.

The report said staff members described the working environment as "being caught between parents going through a bitter divorce."

It put most of the blame on Kuhlman; Jackson was given Kuhlman's post, in addition to running the medical unit, in 2013.

"(M)ost feel that Capt. Jackson's failures were primarily due to the destructive rapport with Capt. Kuhlman and that he has not had the opportunity to lead the WHMU without hindrance or support," according to an excerpt of the inspector general report obtained by NBC News.

At a joint news conference Tuesday with French President Emmanuel Macron, Trump opened the door for Jackson to withdraw his nomination. But it’s not clear that Jackson will decide to leave.

One administration source said Jackson, who believes that the allegations against him are false, has expressed interest in airing it all out at a hearing rather than stepping aside. The expectation is Jackson will make a decision "very soon" — in a matter of days, not weeks.

Two sources told NBC News that prior internal White House reviews found nothing out of the ordinary.

Trump said he had not heard the "particular allegations" against Jackson, calling the Navy doctor a "great leader" and "one of the finest people I've ever met."

Trump said he had told Jackson that the position was not worth the harsh scrutiny he was currently experiencing.

"I told Admiral Jackson just a little while ago, I said, 'What do you need this for?' " said Trump, who met with Jackson earlier in the day in the Oval Office. "This is a vicious group of people that malign, and they do, and I lived through it, we all live through it. You people are getting record ratings because of it, so congratulations. But I said, what do you need it for?"

Trump's original VA secretary, David Shulkin, left the job last month amid an ethics scandal over allegations of excessive and reckless spending, and a subsequent rebellion within the agency.

The president said he did not want to force someone "who's not a political person" through a tough confirmation process.

"I don't want to put a man through a process like this. ... It's too ugly and too disgusting," the president said. "So we’ll see what happens. He'll make a decision."

Asked whether he continued to back his nominee, Trump said he did.

The Senate Veterans Affairs Committee is reviewing the allegations surrounding Jackson's nomination.

Jackson met with lawmakers earlier Tuesday, and later told reporters that he's "disappointed" that his hearing was postponed.

"I’m looking forward to the hearings so we can sit down and I can explain everything to everyone and answer all the senators' questions," he said.

Sen. Jerry Moran, R-Kan., said that Jackson denied allegations of a hostile workplace while working as the White House physician, and told Moran that he has never had a drink while on duty.

Asked about the allegations concerning prescription drugs, Moran said that did not come up during their meeting.