Comcast Corp's (CMCSA.O) merger with Time Warner Cable Inc (TWC.N) is going "full steam ahead" despite uncertainty around new rules governing net neutrality, Comcast Chief Executive Officer Brian Roberts told reporters on Wednesday.

The deal, which would create the largest U.S. cable Internet provider, is in its final phases and remains on track to close, he said at a Comcast press event in San Francisco.

Shares of both companies fell sharply on Monday, after President Barack Obama declared that Internet service providers should be regulated like public utilities, touching off protests from cable and telecoms companies.   

Some analysts thought his comments cast uncertainty over how regulators intended to implement the principle of net neutrality, and in turn cast doubt on the merger deal.

"We are in the final stages of public comment. Sometimes things get slowed down in that phase," Roberts said. "We are full steam ahead."

Opponents to the deal have raised concerns that the sheer size of the eventually merged company would give it too much control over what Americans can watch on television and do online, as Comcast boosts its power as a buyer of web and pay-TV content.

If approved by regulators, the merger would result in a company that would serve just under 30 percent of the U.S. pay television video market. The merged provider would also serve between 20 percent and 40 percent of U.S. broadband subscribers, depending on whether wireless broadband offered by telecom companies is included, Comcast has said.