The 70-year-old's failure to disclose his hospitalization has prompted an extraordinary row in Washington and could be embarrassing for Biden, who faces multiple foreign crises in his reelection campaign year, including in Israel and Ukraine.

As defense secretary, career soldier Austin is personally overseeing military deployments to try and contain fallout from the Israel-Hamas war, which has sparked violence against American forces in Iraq and Syria as well as attacks on international shipping in the Red Sea.

After days of refusal to issue details, the Pentagon came out Tuesday with its first full account of Austin's health issues, but the new transparency came too late for a clearly upset White House.

According to two of his doctors from Walter Reed National Military Medical Center, Austin's prostate cancer was detected as a result of routine screening in early December.

He underwent minor surgery to treat it on December 22, returning home the following day, the doctors said, referring to a procedure the Pentagon had previously been describing as "elective."

However, Austin was readmitted to the same hospital on January 1 due to complications "including nausea with severe abdominal, hip, and leg pain," they said.

"Initial evaluation revealed a urinary tract infection," while medical personnel found "abdominal fluid collections impairing the function of his small intestines" after Austin was moved to intensive care on January 2.

- 'Not good' -

White House National Security Council spokesman John Kirby made clear that Austin had not followed procedures.

"It is not optimal for a situation like this to go as long as it did without the commander-in-chief knowing about it or the national security adviser knowing about it, or frankly other leaders at the Department of Defense," Kirby said during a briefing at the White House.

"It's not the way this is supposed to happen... It's not good. We want to make sure that it doesn't happen again."

Kirby insisted that Biden retains "complete confidence" in Austin and was looking forward to having him back at the Pentagon.

However, amid an outcry both from Democratic allies in Congress and Republican opponents, White House chief of staff Jeff Zients ordered an urgent review of the rules for when senior US officials are incapacitated.

"There's an expectation that if a cabinet officer becomes hospitalized, and for whatever reason can't continue to perform the duties even temporarily, that that will be notified up the chain of command to the commander in chief," Kirby said.

- 'Full recovery' -

The doctors in the Pentagon statement said Austin "continues to make progress and we anticipate a full recovery although this can be a slow process."

The political damage may be as hard to heal.

While Austin was hospitalized on January 1, the Pentagon did not make any public announcement until four days later, and also waited to notify Biden and Congress.

Some of Austin's authorities were transferred to Deputy Defense Secretary Kathleen Hicks on January 2, but she was not told that he was hospitalized until two days later, Pentagon spokesman Major General Pat Ryder told journalists on Monday.

US National Security Advisor Jake Sullivan was informed on January 4, while Congress was not told until the day after that -- the same day the Pentagon made a public announcement, albeit with few details.

Ryder reiterated Tuesday that the secretary has no plans to quit.

Austin "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 the (the Defense Department's) day-to-day operations worldwide," Ryder said.

The defense chief said in a statement over the weekend that he took "full responsibility for my decisions about disclosure," and admitted that he "could have done a better job ensuring the public was appropriately informed."