Comcast has extended its contract to buy wholesale services from AT&T to support its Comcast Digital Voice offering.

Despite the impending merger between AT&T and SBC, with whom Comcast competes, the two companies have agreed to a new contract that establishes AT&T Global Wholesale Services as a key supplier of nationwide transport and termination services.

“Comcast has been a longstanding and important customer for us – we are pretty pleased to continue the relationship,” an AT&T spokesman said.

While neither company is disclosing the terms or the length of the contract, it will go forward after the expected merger date in 2006, he added.

“It’s not unusual at all—we carry traffic for wireless, we provide services to cable industry and to long-distance resellers, all on AT&T’s backbone,” he said. “It is very common for us to be competing at the retail level with companies we provide wholesale services to. This is a great utilization of not just our network capacity but also the types of services we provide, like secure infrastructure and termination. We think this is an important endorsement of the reliability and reach we think we offer.”

Comcast and other cable companies are moving more aggressively this year to deploy voice over IP as part of their service bundle and capture more residential phone lines.