Austin controversially kept US President Joe Biden in the dark about the cancer diagnosis for weeks, and did not inform either the commander-in-chief or Congress until days after he was hospitalized on January 1 for complications from his treatment.

"Secretary Austin was seen today at Walter Reed National Military Medical Center for a scheduled post-prostatectomy surveillance appointment," the doctors said in a statement released by the Pentagon.

"He continues to recover well and is expected to make a full recovery. Secretary Austin's prostate cancer was treated early and effectively, and his prognosis is excellent," they added.

Austin, a 70-year-old career soldier, initially underwent minor surgery to treat the cancer on December 22, returning home the following day.

But he was readmitted due to complications including nausea and severe pain on January 1.

The White House was not informed about Austin's hospitalization until January 4, while Congress was not told until the following day, and Biden did not learn of the cancer diagnosis until January 9.

Austin was released from Walter Reed last week, and made his first public appearance since his hospitalization on Tuesday, speaking via videolink from his residence at the opening of a meeting on aid for Ukraine.

Republican lawmakers have called for Austin to be sacked, but Biden, while lamenting Austin's lapse in judgment, has said he remains confident in his defense secretary.