US cable TV giant Comcast has made a £22.1bn bid for Sky, challenging an existing offer from 21st Century Fox.
Rupert Murdoch’s 21st Century Fox had already agreed an £18.5bn deal to buy the 61% of Sky it does not already own.
Comcast is the biggest US cable TV firm. It also owns the broadcast TV network NBC and Universal Pictures.
Comcast chief executive Brian Roberts called Sky "an outstanding company" and said he was "confident" the offer would be cleared by regulators.
Mr Roberts added that the UK "is and will remain a great place to do business" and that Comcast wanted to "use Sky as a platform for our growth in Europe".
Comcast said Sky News was "an invaluable part of the UK news landscape", and it intended to "maintain Sky News' existing brand and culture".
Mr Roberts added: "We would like to own the whole of Sky and we will be looking to acquire over 50% of the Sky shares".
Comcast said its bid of £12.50 a share was 16% higher than the 21st Century Fox offer.
Fox's Sky bid has not been viewed favourably by the UK's competition authority, which in January provisionally found that it would not be in the public interest.
The Competition and Markets Authority is concerned that if the deal went through, the Murdoch Family Trust would have too much influence over public opinion and the political agenda.
Last week, 21st Century Fox said it would keep Sky News running for at least 10 years, with a fully independent board for the channel, to try to make the proposed deal more attractive to regulators.
The picture was made more complicated in December of last year when Walt Disney agreed to buy the bulk of 21st Century Fox's business, including its 39% Sky stake.
If that acquisition goes through, it could lessen the Murdoch family's UK influence.
Mr Roberts said that Comcast was prepared to co-own Sky with either Fox or Disney, as long as Comcast held a majority stake.