Most of the regulatory experts interviewed last week said they foresaw the deal being approved, but perhaps only with significant conditions attached, as in the News Corporation’s deal for DirecTV in 2003.

Rebecca Arbogast, a managing director at Stifel Nicolaus, a financial services firm that prepared an analysis of the deal last month, said, “They’d take a long and very close look at it.” But, she said, despite the proposed company’s prospective size, “when you sit down and ask yourself, ‘What precisely would be the competitive risks?,’ it has, at least so far, been a bit challenging to think of why the government would view this as being anticompetitive in ways that could not be addressed through conditions, and block it.”

Comcast and NBC Universal executives have not commented publicly, but both companies say privately that they expect approval to take up to a year.

The Federal Communications Commission will be expected to review the deal, but the extent of government regulatory authority is unclear because the terms of the deal itself are unclear.

In part, government action may hinge on whether Comcast intends to sell NBC Universal’s 33 owned-and-operated television stations, 16 of which are NBC affiliates and 17 of which are Telemundo affiliates. The F.C.C. oversees transfers of station licenses. The commission declined to comment last week.

In addition to the F.C.C., the Justice Department or the Federal Trade Commission will also be expected to study the antitrust implications of the deal. The agencies declined to comment.

A crucial concern of public interest groups is so-called vertical integration. By bringing together the makers of programs and the distributors of those programs, the owner could make access to its programming more difficult for its rivals, some interest groups say. Conceivably, they say, Comcast could block its competitors’ access to NBC’s prime-time shows and local newscasts.