U.S. Defense Secretary Lloyd Austin has been diagnosed with prostate cancer, and his hospitalization since the start of this year was due to an infection following a surgical procedure to treat the disease, a military hospital said Tuesday.

A senior White House official said President Joe Biden was not aware that Austin had cancer "until this morning" and that the root cause of his hospitalization was the disease.

U.S. Defense Secretary Lloyd Austin. (Anadolu Agency/Getty/Kyodo)

The announcement by doctors at Walter Reed National Military Medical Center, where Austin has been hospitalized since Jan. 1, and the White House response came as he and the Pentagon have been criticized for going days without reporting his hospitalization to Biden or informing the public.

"Nobody at the White House knew that Secretary Austin had prostate cancer until this morning and the president was informed immediately after," White House national security spokesman John Kirby said during a press briefing.

While noting that Biden has confidence in Austin, Kirby acknowledged that "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."

"That's not the way this is supposed to happen," he said, when pressed by the media why Biden, who spoke with Austin on Saturday, did not know until Tuesday about his disease.

The doctors of the medical center near Washington said in a statement that Austin was admitted with "complications" from the Dec. 22 surgical procedure, which included "nausea with severe abdominal, hip and leg pain."

They said initial evaluation found a urinary tract infection, while disclosing that his prostate cancer was detected in early December and that he later underwent a "minimally invasive surgical procedure called a prostatectomy" to deal with the disease.

During the procedure, Austin was under general anesthesia, according to the statement, which also said his prognosis is "excellent."

The 70-year-old defense chief's secret admission into intensive care at the medical center after being transferred by ambulance on New Year's Day at a time of major security challenges, such as the Israel-Hamas war, has sparked controversy and come under scrutiny by lawmakers, officials and the media.

Biden and his aides were not made aware of those developments surrounding Austin until Thursday. The Pentagon did not inform the public until Friday, and the reason for his hospitalization was not disclosed until Tuesday.

The doctors said further evaluation after the infection was diagnosed showed that Austin had suffered from "abdominal fluid collections impairing the function of his small intestines," adding that he never lost consciousness or received general anesthesia.

They said his infection has cleared but a full recovery can be a gradual process.

According to the Pentagon, Austin has tracked its day-to-day operations worldwide since resuming his duties on Friday evening and has provided necessary guidance to senior staff.

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