A contentious period of public comment regarding Comcast Corp.'s proposed $45 billion deal to acquire Time Warner Cable Inc. ended Tuesday with opponents again calling for the government to reject it and Comcast again saying the deal will lead to public good.

The federal regulatory review of the megadeal - to merge the largest and second-largest cable-TV companies - now enters a negotiation phase that could last through March or April.

Many industry observers believe that the Federal Communications Commission and the U.S. Justice Department will seek conditions on Comcast/Time Warner Cable that would limit its post-merger economic power in the cable-TV and high-speed broadband industries.

But some critics believe that no conditions will be effective and that the deal should be rejected. Both sides - Comcast and its opponents - have spent heavily on lobbyists and media campaigns in Washington.

Jeff Blum, a top Dish Network executive and deputy general counsel, said Tuesday that "there were no benefits, just harm" in the proposed megamerger. He spoke as part of a 45-minute conference organized by a group calling itself Stop Mega Comcast Coalition.

The biggest harm, Blum said, would be Comcast/Time Warner Cable's ability to thwart the efforts of new over-the-top Internet streaming services that could compete with cable-TV.

Dish Network, the nation's third-largest pay-TV operator, has said it will launch an Internet streaming service. Blum said Dish is concerned that Comcast/Time Warner Cable could engage in anticompetitive behavior to hurt that venture.

George Slover, senior policy counsel with Consumers Union, said the merger would lead to higher prices and fewer choices, and would "create a national gatekeeper for broadband."

Comcast says it has answered its critics and that the deal won't lead to the harms opponents fear.

"As in many prior transactions, it is no surprise that various parties have attempted to use this review process to try to advance agendas they may have on industrywide issues and air preexisting grievances that are not related to this transaction," David L. Cohen, Comcast executive vice president and head lobbyist, said Monday in a blog post.

"While these opponents have leveled various allegations, they do not meaningfully contest or contradict the substantial benefits we have demonstrated and supported with compelling evidence."

Groups and individuals can still file comments with the FCC over the merger but they cannot present new arguments against the deal, industry officials said.