The White House is rallying around its nominee to lead the department of Veterans Affairs, who is facing scrutiny over a series of allegations.

A top White House aide said that Donald Trump "will be defending him", as a top senator on the Veterans Affairs committee revealed new claims.

Senator Jon Tester said Dr Jackson was nicknamed "the candy man" because he handed out medications "like candy".

Hours earlier Mr Trump said that he should reconsider if he wants the job.

"If I were him, I wouldn't do it," Mr Trump said on Tuesday during a news conference with French President Emmanuel Macron.

But the tune changed a little later after the president had a meeting with Mr Jackson.

After the two men spoke, the White House director of legislative affairs Marc Short defended Mr Jackson and the vetting process that led to his selection.

No red flags were raised during an FBI background check, he said, adding that the allegations "are false, and we think that Admiral Jackson will do a great job".

Senator Tester, whose Veterans Affairs committee has indefinitely postponed Dr Jackson's confirmation hearing, said that around 20 people have raised concerns regarding his job performance.

He said several have accused him of doling out prescription medications on international flights aboard Air Force One.

"These are called controlled substances for a reason," the Montana Democrat said, adding that his committee needs more time to investigate the numerous allegations.

Mr Jackson has not directly responded to the allegations.

Mr Trump praised the White House physician on Tuesday as "one of the finest people I have ever met", but also acknowledged his nominee's "lack of experience".

"I don't want to put a man... who's not a political person... through a process like this. It's too ugly and too disgusting. So, we'll see what happens," Mr Trump said, seeming to signal an exit door for the embattled nominee.

But after a meeting between Dr Jackson and Mr Trump, the White House doubled down on its support by releasing handwritten notes praising the doctor's job performance.

"Ronny's positive impact cannot be overstated," wrote former president Barack Obama about 50-year-old Iraq War veteran who has worked at the White House since 2006.

"He is a tremendous asset to the entire White House team," he wrote, adding that he should be promoted "now".