As part of its commitment to high-definition TV, CBS is upgrading many of its facilities - including the Ed Sullivan Theater, home of "The Late Show With David Letterman."
But a CBS spokesman said the network has no definitive timetable for completing the conversion.
"We got [HD] cameras in there, but they're not transmitting in HD," the spokesman said.
He did not elaborate on the equipment involved or what obstacles remain for HD broadcasts of the late-night staple.
Last week, CBS announced that HDTV manufacturers Zenith and Samsung would sponsor its primetime lineup of comedies and dramas, all of which are in HD.
