US Defence Secretary Lloyd Austin has cancelled a trip to Nato headquarters after being admitted to hospital for the third time in as many months.
Mr Austin, 70, is in a critical care unit at a Washington DC area hospital. The Pentagon has said he is facing an "emergent bladder issue".
In an update, the Pentagon said they anticipate Mr Austin will be able to resume his duties by Tuesday.
His duties have been transferred to his deputy in the interim.
"A prolonged hospital stay is not anticipated," according to a statement from Walter Reed Military Medical Center officials that was released by the Pentagon on Monday. "We anticipate the Secretary will be able to resume his normal duties tomorrow."
The statement said Mr Austin was in hospital for non-surgical procedures under general anaesthesia to address a bladder issue. He is expected to stay in the intensive care unit at Walter Reed for the duration of his stay, the Pentagon said, but did not indicate how long that stay might be.
Mr Austin has faced scrutiny over the secrecy of his previous hospital admissions.
He had failed to disclose his prostate cancer diagnosis in December or his return to hospital in January, either publicly or to key figures in the US chain of command.
Mr Austin's "current bladder issue is not expected to change his anticipated full recovery. His cancer prognosis remains excellent", Maj Gen Pat Ryder, the Pentagon spokesperson, said.
The defense secretary had been due to lead a meeting of the Ukraine Defence Contact Group (UDCG) in Brussels, Belgium, on Wednesday. It would have been his first overseas trip since his initial hospital admission.
He was also set to attend a meeting of the Nato Defense Ministerial chaired by Nato chief Jens Stoltenberg on Thursday.
Mr Austin attended the last meeting of the UCDG virtually from his home on 23 January.
His office told the BBC that Mr Austin plans to go ahead with these latest scheduled meetings virtually.
On Sunday afternoon, the Pentagon released a statement saying that Mr Austin had been taken to Walter Reed National Military Medical Center in Maryland for treatment, adding that the White House and senior defence officials had been notified.
Later that afternoon, the Pentagon released a second statement saying Mr Austin has "transferred the functions and duties of the office" to Deputy Defence Secretary Kathleen Hicks.
Later on Sunday, the hospital provided an update saying that the secretary had been admitted into the critical care unit "for supportive care and close monitoring".
Officials have not yet said how long the first black US defence secretary will be in hospital or when he might resume his duties.
The bladder issue was not expected to change Mr Austin's "anticipated full recovery" from cancer, his doctors said.
Late last year, Mr Austin had surgery as part of his cancer treatment.
He was readmitted to hospital on New Year's Day with severe pain in his leg, hip and abdomen because of complications related to the procedure. An evaluation found a urinary tract infection and he remained in hospital for more than two weeks.
Senior defence officials and the Biden administration did not know that Mr Austin was seriously ill until three days after his re-admission in January.
The defence secretary is just below the president in the chain of command for the US military, and is regarded as one of the most important members of the cabinet.
The incident stoked concerns over both transparency and security and prompted three separate investigations into Mr Austin's handling of his illness and hospital stays. Some prominent Republicans called for him to be removed from his post.
At a press conference earlier this month, Mr Austin said he was "deeply sorry" for failing to provide appropriate notice and that he had apologised personally to President Joe Biden.
The defence secretary is due to testify at the end of the month about his failure to notify government leaders.