In a sign that the discussions are continuing, neither company nor their lawyers have received signals that the deal would be blocked. Staff lawyers routinely float concerns about a deal but ultimately approve it with some conditions. Early objections against a deal can serve as a negotiating tactic to get a company to come to the table.

Comcast has not yet started negotiations with regulators about potential conditions to place on the deal, according to one person with knowledge of the discussions. Even if regulators blessed the merger, they could demand arduous conditions from Comcast, like having to divest itself of more subscribers. If that occurred, Comcast could walk away from the deal, which has no breakup fee.

Multiple television executives who do business with the two cable giants said that they have been in frequent communication with regulators during the review process, and that in recent days government lawyers have narrowed their line of questioning. That has led them to think that the agency is trying to uncover evidence that would shore up their argument for why the deal would be anticompetitive.

One specific question asked this week was whether Comcast and Time Warner Cable compete with the television companies to distribute programming to consumers, one person with knowledge of the discussions said. Networks like HBO and CBS, for instance, recently introduced new Internet streaming services that offer access to their content without a traditional cable subscription.

Image A merger of Comcast and Time Warner Cable would unite the largest cable operators in the United States. Credit... Joe Raedle/Getty Images

The staff lawyers will ultimately present their recommendation to the senior officials in the Justice Department’s antitrust division. In this instance, though, William J. Baer, who leads the antitrust division, is recused from the case. When Mr. Baer was in private practice, he worked on the Comcast acquisition of NBCUniversal.