In a statement, Senate VA committee chairman Johnny Isakson, a Georgia Republican, and Jon Tester of Montana, the top Democrat on the panel, said: "We take very seriously our constitutional duty to thoroughly and carefully vet each nominee sent to the Senate for confirmation".
Though the White House publicly defended Jackson on Tuesday, several officials have privately conceded that the President's nominee to lead the Veterans Affairs department is in trouble.
President Trump says he still supports his White House physician, but left the door open for Jackson to withdraw his nomination.
"I'd let it be his choice", said Trump, who called him "an extraordinary person".
Jackson, the White House physician and a former combat surgeon, was scheduled to testify before the Senate Committee on Veterans' Affairs on Wednesday.
I said to him, what do you need it for?
According to CNN, sources said that Jackson's nomination could be in jeopardy following the allegations.
"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.
"No matter whether these allegations against Dr. Jackson prove true or false, whether they continue to delay his confirmation indefinitely or sink it altogether, it's the latest in a chain of unforced errors for which veterans are continuing to pay the price", said AMVETS National Executive Director Joe Chenelly.
The Trump administration is standing behind Jackson, who also faces questions about his qualifications to manage the federal government's second-largest department. But it is unclear when, or if, the hearing will be rescheduled.
"He does deny that he's done anything wrong in his service to the country and particularly his time at the White House as a physician in the medical unit", Moran said. It demands any communication between the Pentagon and the White House for the past 12 years regarding "allegations or incidents" involving him.
"So he'll be making, it's totally his decision, but he'll be making a decision, ' Trump continued".
Deputy secretary Hogan Gidley released a statement Tuesday morning on Jackson after news of the allegations broke, saying "He's served as the physician to three Presidents-Republican and Democrat-and been praised by them all".
Senate Majority Leader Mitch McConnell (R-Ky.) told reporters Tuesday that he is not sure if Jackson will receive a hearing.
Trump said he would stand behind Dr. Ronny Jackson, calling the White House doctor "one of the finest people that I have met".
"I think the White House has to give us full, and accurate, factual responses completely addressing these questions, today".
Sen. Sherrod Brown, D-Ohio, who sits on the VA committee, said the number of people who came forward with allegations is in the double digits.
So yes, in one sense, it was reasonable that Trump would ask why Jackson would want a post for which he was completely unqualified, or be willing to endure the process of getting it.
"Remember the way the President has insulted President Obama's treatment of veterans". "We're vetting hard right now", he said. Instead, the officials insisted Jackson would push back forcefully and said Trump was not wobbling over his selection.
He added: "You could run the biggest hospital system in the world and it's small-time compared to the veterans administration".