Shari Redstone, whose National Amusements controls CBS and Viacom, is likely to replace CBS CEO Les Moonves if a deal isn't reached between the two companies as the media tie-up hits an impasse, sources familiar with the situation said.

CBS is expected to make another offer soon, the sources said, but that new bid was expected to fall short on price. The amount of synergy expected by CBS is well below that of Viacom.

The main obstacle to the rejoining of the network and owner of Nickelodeon and MTV is a growing distrust between Redstone and Moonves. As CNBC previously reported, Moonves wants to pick his own management team if he is to head the combined entity and favors Joe Ianniello, chief operating officer of CBS, as his key lieutenant. Redstone, however, wants Bob Bakish, the current CEO of Viacom, as No. 2.