The Pentagon announced on Tuesday that U.S. Defense Secretary Lloyd Austin had been in the hospital due to a urinary tract infection following a December surgical procedure to treat prostate cancer.

The disclosure comes after nearly a week in which the Defense Department faced public backlash over the secrecy surrounding Austin's whereabouts, with even President Joe Biden kept in the dark for days.

The Pentagon last Friday said Austin had been hospitalized, but declined to say why.

RYDER: "Secretary Austin continues to recover well and remains in good spirits. He's in contact with his senior staff and has full access to required secure communications capabilities and continues to monitor DoD's operations worldwide."

Austin, who is 70, sits just below Biden at the top of the U.S. military's chain of command, and his duties require him to be available at a moment's notice to respond to any national security crisis.

His handling of the situation appeared to be a stark breach of protocol for high-ranking cabinet officials, who typically inform the public of planned medical absences ahead of time and identify who will be filling in for them.

Austin may have also violated internal U.S. Department of Defense protocols, and officials say they are conducting a full review of the incident to determine how future lapses could be prevented.

Biden's national security council spokesperson John Kirby faced questions on Tuesday about how the president, who is running for re-election, did not know of his defense secretary's Jan. 1 hospitalization until days later.

QUESTION: "The president has known, for I guess five days now, that Secretary was in the hospital, but he wasn't informed why?"

KIRBY: "He was not informed until last Friday that Secretary Austin was in the hospital. He was not informed until this morning that the root cause of the hospitalization was prostate cancer."

The Pentagon has said the White House also did not know about Austin's original December treatment for what it initially said was an elective medical procedure.

Some prominent Republicans, including former President Donald Trump, called for Austin to be removed from his job, but for now the administration is sticking with the defense chief.

QUESTION: "Does the president plant to stick with Secretary Austin through the rest of the term?"

KIRBY: "Yes."

The White House on Tuesday said in a memo that the administration is conducting a review of Cabinet protocols for delegating authority.