– President Donald Trump acknowledged Tuesday that Dr. Ronny Jackson, his nominee to lead the Veterans Affairs Department, is in serious trouble amid allegations that he oversaw a hostile work environment as the White House doctor, allowed the overprescribing of drugs and possibly drank on the job.

Speaking at a midday news conference with the president of France, Trump strongly defended Jackson, the White House physician, as “one of the finest people that I have met,” but he hinted that Jackson might soon withdraw from consideration, blaming Democrats for mounting an unfair attack on his nominee’s record.

“I don’t want to put a man through a process like this,” Trump said. “The fact is, I wouldn’t do it. What does he need it for?”

By Tuesday evening, however, Trump and Jackson met face-to-face, and the White House moved aggressively to defend the doctor against what the president had called “ugly” abuse by politicians. A White House statement said that Jackson’s record was “impeccable” and insisted that he would not be “railroaded” by false accusations.

The concern over Jackson’s nomination is bipartisan and emerged after Senate Veterans’ Affairs Committee interviews with more than 20 people, including current and former military personnel who had worked with him. The committee began an investigation last week into Jackson’s White House work record, and its Republican and Democratic leaders jointly announced Tuesday that his confirmation hearing, planned for Wednesday, would be postponed indefinitely “in light of new information presented to the committee.”

“We take very seriously our constitutional duty to thoroughly and carefully vet each nominee sent to the Senate for confirmation,” said Sens. Johnny Isakson, R-Ga., the committee chairman, and Jon Tester of Montana, its top Democrat, in a joint statement. “We will continue looking into these serious allegations.”

Jackson, speaking with reporters on Capitol Hill before meeting with a Republican senator Tuesday afternoon, gave no indication that he would withdraw his nomination. He also did not deny or answer questions about the accusations.

Members of Tester’s staff said that they had been given several credible accounts of Jackson being intoxicated during official White House travel.

On one trip during Barack Obama’s presidency, White House staff needed to reach Jackson for medical reasons and found him passed out in his hotel room after a night of drinking, Tester aides said. The staff members took the medical supplies they were looking for without waking Jackson.

Tester said that there was no evidence before the committee that Dr. Jackson had shown up drunk to the White House.

In response, White House officials described Jackson’s record as “impeccable,” and they distributed glowing comments that they said Obama wrote in Jackson’s annual military performance review.

“Ronny does a great job — genuine enthusiasm, poised under pressure, incredible work ethic and follow through,” Obama said of Jackson in 2016, according to information released Tuesday evening by White House officials.

Members of both parties also pushed back on the alcohol accusation. Senator Jerry Moran, Republican of Kansas, said that Jackson told him on Tuesday that “he has never had a drink while on duty.”

Brian McKeon, who served as chief of staff for the Obama National Security Council, said he does not recall Dr. Jackson ever drinking to excess.

Tester said the committee had also received reports of a “toxic work environment” at the White House medical unit, which Jackson has overseen since 2013.

“That would involve belittling, screaming, verbally abusing the staff to the point where he would explode and the staff would feel they were on eggshells,” Tester said.

Tester said that the committee had also received credible accusations that Jackson routinely distributed Ambien, a prescription sleep aid, to White House staff and members of the news media flying on long overseas trips, as well as Provigil, a prescription drug for promoting wakefulness.

Tester said that he had spoken with John Kelly, the White House chief of staff, about the charges on Monday. Kelly, he said, told him that the distribution of sleep aids and wakefulness drugs was “standard operating procedure.” Tester said he disagreed.