Cingular Wireless LLC and AT&T Wireless Services Inc., which plan to merge, have agreed to pay $175 million and give up some cellular capacity elsewhere to strengthen their signals in Virginia, according to a source close to the companies.

The cell phone companies would turn over some of their cellular network in North Carolina and Puerto Rico in exchange for Triton PCS Holdings Inc.'s network in Virginia, which includes Richmond, Roanoke, Charlottesville and Norfolk, according to the source, who requested anonymity because the deal is scheduled to be announced today.

Cingular, which hopes to close its $41 billion merger with AT&T Wireless by the end of the year, does not have any airwave licenses in those parts of Virginia. It has had to rely on roaming agreements with other carriers for its customers to get service in those areas.

The deal would reduce the roaming charges paid by some Cingular customers, as well as the amount the company has to pay to send phone calls over other carriers' networks. AT&T Wireless also would return its 17 percent ownership in Triton to the company in exchange for an agreement to pay lower rates to use Triton's network.

In addition, Cingular would get Triton's 400,000 Virginia customers and 300 employees in Virginia. Roughly the same number of AT&T Wireless employees and customers in North Carolina and Puerto Rico would transfer to Triton. That transfer would not occur until Cingular's merger with AT&T Wireless is complete.

Atlanta-based Cingular hopes that saying it would divest network and assets to Triton will help its merger win regulatory approval. The combined Cingular and AT&T Wireless would be the dominant carrier in some North Carolina markets. The merger is under antitrust review by the Department of Justice and the Federal Communications Commission.

Triton, based in Berwyn, Pa., is an affiliate company with agreements to allow its customers to use AT&T Wireless's network outside of Triton's coverage area. AT&T Wireless customers also roam onto Triton's network. As of March 31, Triton had 919,906 customers in the Southeast. It plans to continue to provide the reciprocal roaming agreements.