Austin has been hospitalized since January 1 for complications from prostate cancer treatment, but did not inform the White House or Congress for several days after he was admitted, sparking calls for him to leave office and raising questions about how significant a role he is playing on national security issues.

"He was fully engaged even from his hospital bed," National Security Council spokesman John Kirby told MSNBC, adding that Austin "was involved actively and intimately all day yesterday with the national security team here at the White House and of course with the commander-in-chief, with President Biden."

"The president has made it clear: Secretary Austin is his defense secretary, will remain his defense secretary. He has full faith and confidence in in Secretary Austin and his leadership," Kirby said.

"That leadership... was on display to everybody in the national security team as he in a hospital bed still leading and commanding our forces in some dangerous missions here," he added.

The Huthis have carried out a growing number of drone and missile strikes on the key international route through the Red Sea since the Gaza war erupted with Hamas's unprecedented October 7 attack on Israel.

The rebels ignored a warning from the US and other countries last week of consequences if they did not halt the attacks, and Washington and London's forces carried out strikes against dozens of targets in Yemen overnight.