AOL Warner is preparing a plan to challenge incumbent carriers on their home turf with a rollout of voice-over-IP service either later this year or early next year.

Speaking at the Morgan Stanley Global Media & Communications Conference this week, Wayne Pace, AOL Time Warner’s chief financial officer, said executives are preparing a rollout plan to present to the board of directors. “We’re looking to consider aggressively getting more into the voice business,” Pace said. The company’s cable operator group has been testing VoIP service in Portland, Maine, for much of this year and has about 4000 customers, he added.

Though no longer the largest cable operator in the country, a move by Time Warner into VoIP would be significant because of the number of large markets it serves, particularly on the East Coast. At the same time, any vendor winning the endorsement of the multiple system operator would have a significant customer to use as currency in future bids.

“We’re comfortable with the technology and we believe that the opportunity to bundle voice with video and data is very strong,” Pace said.

Thus far, CableLabs has certified four softswitch vendors under its PacketCable program, which is designed to provide pre-qualification for the entire U.S. cable industry. The vendors to get PacketCable 1.0 approval are Cedar Point Communications, Cisco Systems, Nortel Networks and Syndeo.