Kansas City, Mo. ? Shares of Sprint Corp. and Nextel Communications Inc. jumped Thursday following reports the two telephone companies were discussing a merger.

Sprint stock gained $1.78 per share, or 7.9 percent, on heavy volume to close at $24.28 on the New York Stock Exchange. Nextel, trading at four times its normal volume on the Nasdaq Stock Market, gained $1.84, or 6.6 percent, to finish at $29.81.

Both companies, frequently mentioned as suitable merger partners, declined comment on the reports.

The Wall Street Journal reported on the prospect of a merger in Thursday’s editions. Later in the day, The Journal reported on its Web site that negotiations were underway.

Overland Park-based Sprint is the nation’s third largest cellular company in terms of subscribers, and is a major provider of local and long-distance telephone service for homes and businesses.

Reston, Va.-based Nextel — the fifth largest wireless company and the only national cellular provider that’s an independent entity — is especially popular among spread-out groups of workers who use the walkie-talkie feature on Nextel’s phones to keep in constant contact.

A merger would create an entity with more than 38 million wireless subscribers, making it a more potent rival to Cingular Wireless and Verizon Wireless by allowing the combined company to pool resources and cut costs.

It also would give Sprint a better presence in business markets while providing more bandwidth and advanced services for Nextel, which does not have a high-speed wireless Internet offering like Sprint.

“There are some reasons why it would make sense,” said Mark Hesse-Withbroe, who helps manage $125 billion of investments at U.S. Bancorp Asset Management in Minneapolis, including Sprint shares. “Among the Nextel, Sprint, Verizon camp, it’s probably where a merger would most likely take place.”

Sprint would gain access to Nextel’s business customers, who pay higher monthly bills and are more loyal than customers of any other national wireless carrier. Nextel’s average monthly bills were $69 and its monthly rate of customer turnover was 1.5 percent in the third quarter, compared with Sprint’s $63 in average monthly bills and churn of 2.7 percent.

Nextel loses a smaller percentage of subscribers than any other mobile-phone company in part because it sells a combined walkie-talkie wireless service that outperforms competitors’ own versions, analysts and investors have said.

Cingular, a joint venture between SBC Communications Inc. and BellSouth Corp., recently completed its acquisition of AT&T Wireless to become the nation’s biggest cell company with 47.25 million customers. Verizon Wireless, a partnership between Verizon Communications Inc. and Vodafone Group PLC, is the second largest with about 42 million subscribers.

Through the first nine months of this year, Nextel earned $2.48 billion on $9.79 billion in revenue. During the same period, Sprint brought in $20.5 billion in revenue but reported a $1.46 billion loss after taking a $3.5 billion charge on the value of its long-distance assets.

The Journal said a possible deal could involve Sprint spinning off its local-phone service to a separate company, allowing it to focus on the wireless business. Sprint is the local-phone company in parts of 18 states and has about 7.8 million access lines.

Sprint recently has moved away from standalone products and has focused on selling packages that include traditional phone, wireless and high-speed Internet services.

Jeffrey Kagan, an independent telecommunications analyst in Atlanta, said he expected Sprint would not abandon traditional phone service, which the company could provide through Internet telephone technology.

“There’s a move towards everything being on the same line,” he said.