U.S. Defense Secretary Lloyd Austin on Thursday took full responsibility for keeping President Joe Biden in the dark for weeks that he had been diagnosed with prostate cancer, saying he never directed anyone in his staff to keep his January hospitalization from the White House or the public a secret.

"We did not handle this right and I did not handle this right. I should have told the president about my cancer diagnosis. I take full responsibility," Austin said.

"The news shook me," Austin, 70, said when he first got the diagnosis. "Frankly my first instinct was to keep it private."

Speaking to reporters in the Pentagon briefing room, Austin provided his most extensive comments to date on the secrecy surrounding his cancer diagnosis and struggles with complications since his surgery on Dec. 22. It was the first time he had answered questions from reporters since being rushed back to the hospital on Jan. 1.

"I never directed anyone to keep my January hospitalization from the White House," Austin said.

Known as a very private person, Austin appeared calm as he fielded a barrage of questions about his health and why he failed to inform the president and other key leaders about his hospitalizations until days after he was admitted to intensive care.

His lack of disclosure prompted changes in federal guidelines and triggered an internal Pentagon review and an inspector general review of his department’s notification procedures. Both reviews are ongoing, and members of Congress have called for hearings on the matter.

Austin was diagnosed with prostate cancer early in December and had surgery on Dec. 22. On Jan. 1, he was taken by ambulance to Walter Reed National Military Medical Center after experiencing extreme pain due to complications from the surgery and was admitted to the intensive care unit.

He transferred decision-making authorities to Deputy Defense Secretary Kathleen Hicks, but did not tell her why. He also did not tell Biden and other top officials about his diagnosis, his surgery, or hospitalization until several days after he was in the ICU.

Asked about the matter earlier in January, Biden said it was a lapse in judgment for Austin not to tell him about his hospitalization, but he said he still has confidence in his Pentagon chief.

Austin, who worked from home for two weeks after his release from the hospital Jan. 15, returned to work in the Pentagon on Monday. He had not been in the building since Dec. 21.

Underscoring the secrecy surrounding Austin's hospital visit, one of his aides asked first responders to avoid using lights and sirens when requesting an ambulance be sent to the secretary's northern Virginia home on Jan. 1.