WASHINGTON -- US Secretary of Defense Lloyd Austin was admitted into the critical care unit at Walter Reed National Military Medical Center for supportive care and close monitoring on Sunday night, said a US Defense Department statement.

Earlier in the day, the department announced that the secretary was sent to the medical center in Washington D.C. for a bladder issue, noting that his duties have been transferred to his deputy, Deputy Defense Secretary Kathleen Hicks.

Recently, Austin was hospitalized due to complications after surgery. Failing to promptly inform the White House and Congress caused a significant political and public uproar.

Pentagon spokesman Patrick Ryder said that Austin's latest hospitalization has been notified to the White House, the Joint Chiefs of Staff, and Congress.

Austin, 70, underwent surgery on Dec 22 last year and temporarily transferred some of his authorities to Hicks.

On Jan 1 this year, due to a worsening condition, he was sent to Walter Reed National Military Medical Center and admitted to the intensive care unit. President Joe Biden and other senior officials were not informed of the situation until Jan 4.

In response to criticisms over the concealment, Austin publicly apologized on Jan 6.

Later, the medical center detailed Austin's hospitalization, revealing that he was diagnosed with prostate cancer in December and underwent a minimally invasive surgery called prostatectomy.

As a key member of the president's Cabinet and the National Security Council, the defense secretary is the primary formulator of US defense policy and a crucial link in the US military chain of command.

After the concealment incident, the US political circles criticized Austin and the Pentagon. Republicans, in particular, directed their criticism at the Democratic government, demanding Austin's resignation.