Conservative commentator Robert Novak has announced that he has retired from his post at the Chicago Sun-Times effectively immediately. Novak's retirement comes just one week after having been diagnosed with a brain tumor, and now describes the prognosis as "dire".

Novak told the paper, "The details are being worked out with the doctors this week, but the tentative plan is for radiation and chemotherapy." He will undergo treatment at the National Cancer Institute in Washington D.C.

It is not yet known whether or not Novak will end his regular appearances on national television programs.

Novak, 77, contributed his final column to the Sun-Times on Sunday, July 27. He has been with the paper since 1966, and his column was first syndicated in 1963 by Publishers Newspaper Syndicate.

Two weeks ago Novak was cited for a hit and run after hitting a pedestrian in a Washington D.C crosswalk. At the time of the incident he said he wasn't even aware he had hit anyone. It is not known if the brain tumor contributed to the accident.