US lawmakers and both presidential candidates have raised questions about AT&T’s deal to buy Time Warner.
The US telecoms giant, already the country’s third largest cable provider, is paying $85.4bn (£70bn) for the company, which owns CNN and HBO.
A Senate subcommittee responsible for competition will hold a hearing in November.
However, AT&T’s chief executive Randall Stephenson believes regulators will approve the deal.
Senator Mike Lee, the Republican who chairs the antitrust subcommittee, said the deal would “potentially raise significant antitrust issues, which the subcommittee would carefully examine”.
The biggest merger to be announced this year would combine AT&T’s distribution network, which includes 130m mobile phone customers and 25m pay-TV subscribers, with content from the Warner Brothers film studios and the cable TV channels HBO, the Cartoon Network and CNN.
The competition concerns centre on higher prices for customers and less consumer choice.