"The president has complete confidence, continues to have confidence in Secretary Austin," Press Secretary Karine Jean-Pierre told reporters travelling with Biden aboard Air Force One.

"The number one thing is we want to see him get well and back at the Pentagon."

Republicans have called for Austin to resign or be sacked after it emerged that Biden and the White House were unaware for several days that he had been hospitalized for an unspecified medical condition last week.

White House National Security Council spokesman John Kirby said Biden believed Austin had done an "amazing job" and respected Austin for "taking ownership" of the row.

"There is no plans or anything other than for Secretary Austin to stay in the job and continuing the leadership that has been exhibited," Kirby told the same briefing.

"We'll do what's akin to a hot wash and try to see if processes and procedures need to be changed at all or modified, so that we can learn from this."

Austin had resumed his duties and was working from the Walter Reed military hospital in the Washington suburbs, added Kirby.

The spokesman would not comment on what Biden now knew about Austin's medical condition.

The Pentagon waited until Friday evening to announce that Austin, 70, had been hospitalized four days prior "for complications following a recent elective medical procedure" -- a breach of standard protocol at a time when the United States is embroiled in the Middle East crisis.

"I recognize I could have done a better job ensuring the public was appropriately informed. I commit to doing better," Austin said in a statement on Saturday.