David Burke, president of the CBS News division, will be leaving this week, sources at the network said Wednesday night. Burke, 54, a former ABC News executive vice president who joined CBS in August 1988, didn't return phone calls Wednesday night, nor did Tom Goodman, Burke's chief spokesman. It was unclear if Burke was being forced out or was resigning of his own accord. One CBS source, who spoke on condition of anonymity, quoted network executives as saying the reclusive Burke had told them he was leaving, but gave no reason. ``Nobody seems to know why he's going,'' the source said. Another source, speaking of Burke's imminent departure, said Burke has had philosophical differences with CBS Inc. President Laurence A. Tisch. Pressure from Tisch to cut costs at CBS News led to the firing of more than 200 staffers in 1987. Tisch didn't return phone calls. Burke's departure may be announced Thursday, sources said. Speculation on his likely successor includes Eric Ober, a former CBS News executive who now heads the company's stations division. CBS News, after more than five years of well-publicized internal turmoil, recently had been scoring successes with its coverage of the Persian Gulf crisis, highlighted by anchorman Dan Rather's reports from Iraq. While the revamped ``CBS Morning News'' has remained third in morning news show ratings, Rather's ``CBS Evening News'' has been a respectable second to ABC's ``World News Tonight'' for several months. Burke, a former top aide to Sen. Edward M. Kennedy, D-Mass., came into the news business late in his career when hired by ABC News President Roone Arledge. At CBS News, Burke succeeded Howard Stringer, who now is president of the CBS Broadcast Group and headed CBS news after the ouster of Van Gordon Sauter, now a TV producer in Los Angeles. There had been rumors for several weeks within CBS News that Burke was leaving. But when asked about them earlier Wednesday, Goodman, his spokesman, said that as far as he knew there was nothing to them. Burke's exit would mark the second high-level change in network news this summer. Earlier this month, former Los Angeles Times Publisher Tom Johnson succeeded Burt Reinhardt, 70, as president of Ted Turner's Atlanta-based Cable News Network.