"I do feel you should have as many news outlets as you can - especially since so many are fake", Trump continued, according to a pool report.
Previously, the president has blasted AT&T and Time Warner's merger plans - and during the 2016 election he threatened to block the companies from combining under his watch.
Speaking at a conference in New York, Stephenson disputed claims he offered to sell CNN to win approval of AT&T's takeover of Time Warner.
President Donald Trump appeared to stress on Saturday that he had not intervened in AT&T's bid to buy Time Warner - or sought to require that the companies sell CNN in order to obtain the US government's approval of the deal.More news: EA to acquire Titanfall developer Respawn Entertainment
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Raj Shah, a White House spokesman, said in a separate statement that Trump "did not speak with the Attorney General about this matter, and no White House official was authorized speak with the Department of Justice on this matter".
Nevertheless, a group of eight Democratic US senators on Friday wrote to Makan Delrahim, head of the Justice Department's antitrust division, urging the department "to oppose any attempt by the White House to interfere with antitrust law enforcement decisions, particularly for political reasons". CNN has been a favorite punching bag for Trump, who has maligned the network repeatedly on the campaign trail, after winning last year's election, and since taking office this January. AT&T stock closed up 1.1 percent at $33.44. The agency has a decades-long history of approving similar deals, including the merger of Comcast and NBCUniversal in 2011. It would then supply its video - HBO, CNN, TBS and the Warner Bros. movie studio - while providing access to the internet for millions of Americans.
The president has frequently referred to CNN as "fake news".
Being forced to sell off Turner is probably a "nonstarter" for AT&T, New Street Research analyst Jonathan Chaplin said. "It's hard to imagine an antitrust argument that will be compelling" from the government, he said. "Beyond that, the Department does not comment on any pending investigation".