Lisa Nandy has said she is "minded to intervene" in the proposed £1.6bn deal for Sky to buy ITV's media and entertainment division.
The culture secretary said there were reasonable grounds to believe the deal could affect free expression in the media and the variety of Britain's news landscape.
Sky said it would "carefully consider" a letter from Nandy and "engage constructively" with the review into the deal.
"We remain confident that bringing Sky and ITV's media and entertainment business together will create a stronger British media," it said.
The two companies announced in July that Sky had agreed to buy ITV's broadcasting business, including its free-to-air TV channels and the ITV X streaming service.
The deal does not include ITV's production arm, ITV Studios, which makes popular programmes such as Love Island and I'm a Celebrity... Get Me Out of Here.
Nandy has told Sky and ITV that she is considering issuing a public interest intervention notice (PIIN) to the competition watchdog, forcing it to investigate the tie-up.
A Sky spokesperson said: "We have already made clear commitments to protect ITV's identity, its free-to-air services and public service broadcasting obligations, and to ensure ITV News and Sky News remain distinct editorial voices."
