Rupert Murdoch's 21st Century Fox has reportedly made an $80 billion bid for Time Warner. The New York Times reports that the bid was declined, citing "people briefed on the matter." It's unclear if Fox will return with a higher offer, but the NYT's sources say Murdoch is "determined" to push ahead with the takeover and is unlikely to walk away. In the initial proposal, Fox reportedly indicated it would sell CNN as part of the deal. Fox News and CNN are direct competitors, and a sale could potentially avoid antitrust concerns.

Even without CNN, bringing Time Warner's immense business under the 21st Century Fox banner would turn Murdoch's into a truly colossal media company. Fox would control the output of the Warner Bros. production and distribution business for TV shows and movies, the Turner TV portfolio (which includes NBA and MLB broadcast rights), and HBO.

In the wake of the NYT's story, CNBC has confirmed the offer and rebuttal with 21st Century Fox. CNBC says the two company's CEOs met in June to discuss a potential deal, before Fox was sent a rejection letter earlier this month. Although the two companies are reportedly not currently in discussions, Time Warner could now face pressure from shareholders to take any future offers very seriously, given the public exposure of the takeover bids. Shares of Time Warner jumped over 12 percent in premarket trading following the revelation.

Any deal between Fox and Time Warner would be entirely separate from the proposed and controversial Comcast-Time Warner Cable merger: the cable side of Time Warner's business became a separate entity in 2009.