The Pentagon failed to notify US President Joe Biden for days that Austin was in hospital with complications from treatment, at a time of high tensions in the Middle East and Ukraine.

"The White House is conducting a review of agency protocols for a delegation of authority from cabinet members," said a memo from Biden's chief of staff Jeff Zients, obtained by AFP.

The memo said government departments "must ensure" they stick to current procedures, particularly on notifying the White House if a cabinet minister has to delegate authority for any reason.

Departments must also submit their delegation processes for review by Friday to ensure they are fit for purpose, the memo said.

Austin has faced Republican calls to resign or be sacked over the row.

The Pentagon announced last Friday, for the first time, that he had been hospitalized since the preceding Monday. It later emerged that the White House had not known until that Thursday.

Finally on Tuesday the Pentagon said Austin had been treated for prostate cancer.

It said the disease was detected early and his prognosis was "excellent" after he had a surgical procedure under general anesthetic on December 22, but that he was readmitted to intensive care with "complications," including an infection, nausea and severe abdominal, hip, and leg pain.