Officials at a US prison hospital on Wednesday said chronic medical problems were complicating a psychiatric evaluation for an 89-year-old man accused of fatally shooting a guard at Washington's Holocaust museum.

US District Judge Reggie B. Walton granted an eight-week extension for the evaluation of James von Brunn. Walton said the warden at Butner Federal Medical Center in North Carolina requested the extension because several chronic ailments were preventing officials from conducting necessary tests.

The report on von Brunn's competency to stand trial had been expected at the end of November. Monday's order extends von Brunn's time at Butner to January 2.

Von Brunn is accused of killing Stephen T. Johns at the US Holocaust Memorial Museum on June 10.