BellSouth Corp. has entered the bidding for Sprint Corp., the nation's third-largest long-distance company, seeking to pry it from MCI WorldCom Inc., which has come close to a deal in ongoing merger talks with Sprint, sources with knowledge of the talks said last night.

BellSouth's entry complicates MCI's efforts to complete a deal that would stand as the latest in a series of monster mergers that have reshaped the communications industry. MCI has come to see Sprint as the potential long-sought fix to a glaring deficiency--its lack of presence in the fast-growing world of wireless telephone service. Sprint boasts Sprint PCS, a national all-digital cellular network.

An executive with one of the companies said rumors of BellSouth's interest in acquiring Sprint have been heard widely since the spring, when the former head of Sprint's long-distance division moved to a senior position at Bell South. BellSouth did not return phone calls last night, and a Sprint spokesman declined to comment. In addition to its long-distance and wireless business, Sprint owns a sizable data network and several local phone systems in North Carolina, Florida, Virginia and Las Vegas. While those companies would be of little interest to MCI--which is focusing on the nation's largest markets as it expands into local service--they could well interest BellSouth, which is based in Atlanta.

BellSouth is particularly keen to gain Sprint's long-distance stature as it presses ahead with plans to enter the long-distance market, the executive said.

An analyst suggested BellSouth and MCI could wind up splitting Sprint, with MCI claiming the cellular network and BellSouth the local companies and the data network. Sources at the Federal Communications Commission say an MCI-Sprint merger could require a sell-off of data networks to gain regulatory approval.