CNN confirmed Monday that Campbell Brown, the former NBC Weekend Today co-anchor, is joining the cable news network and will host a news program in primetime, but it did not disclose which existing program Brown's will replace. Meeting with reporters covering the TV business, CNN (U.S.) President Jon Klein said that while a decision about Brown's timeslot had been made, "we want to wait for the most appropriate time" to disclose it. Most writers have assumed that Brown will be replacing Paula Zahn, whose ratings in the 8:00 p.m. hour have disintegrated against the juggernaut that is Bill O'Reilly on Fox News. What is not known is whether CNN will move another one of its primetime anchors into that slot -- Lou Dobbs, say, or Anderson Cooper -- and have Brown take over their time period. Under her exit deal with NBC, Brown cannot appear on CNN until November. Complicating matters further is the fact that Brown is due to deliver her first child one month later. Meanwhile, CBS announced on Monday that it had hired Dean Reynolds, an ABC correspondent and son of the late ABC World News Tonight anchor Frank Reynolds, to head its Chicago bureau.