U.S. Secretary of Defense Lloyd Austin was admitted to a critical care unit in Washington on Sunday for treatment of "symptoms suggesting an emergent bladder issue", officials of Walter Reed Military Medical Center said, Paralel.Az reports citing Reuters.

Austin, 70, later transferred the duties of his office to Deputy Secretary of Defense Kathleen Hicks, Pentagon Press Secretary Major General Pat Ryder said in a statement.

Both Republican and Democratic lawmakers criticized Austin last month for failing to disclose a cancer diagnosis and subsequent hospitalizations in December and January, including to President Joe Biden. Some prominent Republicans, including former President Donald Trump, called for Austin to be removed from his job.

Austin apologized during a televised news briefing. He is scheduled to testify before Congress on Feb. 29 about the situation.

Biden, a Democrat, has said he has confidence in Austin despite what the president agreed was a lapse in judgment.

With its announcement of the secretary's trip to the hospital and the quick decision to transfer his duties to a deputy, the Pentagon appeared determined to avoid a repeat of last month's political uproar.

It was unclear how long Austin would remain hospitalized, officials of the hospital said in a statement late on Sunday.

Austin's cancer prognosis remained excellent and the bladder issue was not expected to change his anticipated full recovery, the officials added.

Austin, a retired four-star general who led forces in Iraq and is America's first Black defense secretary, was still in hospital last month as U.S. forces launched a retaliatory strike against a militia leader in Baghdad.

There are now three different investigations into Austin's behavior, including one by the office of the Pentagon's Inspector General, a watchdog agency that tracks military waste, fraud and abuse. The Republican chair of the House Armed Services Committee, Mike Rogers, has called Austin to testify.

Austin is scheduled to travel to Brussels for a Wednesday meeting of the Ukraine Defense Contact Group. It was not clear if his hospitalization would affect those travel plans.