Comcast, which owns NBC and Universal Pictures, said it was offering 12.50 pounds per share. That proposal is significantly higher than the 10.75 pounds per share agreed by Twenty-First Century Fox.
"We think Sky is an outstanding company. It has 23 million customers and leading positions in the U.K., Italy, and Germany," Comcast Chairman and CEO Brian L. Roberts said in a statement.
"Sky has been a consistent innovator in its use of technology to deliver a fantastic viewing experience and has a proud record of investment in news and programming. It has great people and a very strong and capable management team."
U.K.-listed shares of Sky surged 20 percent on Tuesday morning. Comcast indicated that it will be looking to acquire over 50 percent of Sky's shares.
In a conference call with investors Tuesday morning, Roberts said a Comcast-Sky deal would be a "perfect fit" that could create a "unique leader" in entertainment and technology.
He added that the U.K. will remain a great place to do business and said Comcast intends to use Sky as a platform for the company's growth in Europe.
"We intend to maintain and enhance Sky's business. Adding Sky to the Comcast family of businesses will increase our international revenues from 9 percent to 25 percent. We believe that there are significant opportunities for growth by combining these businesses," he said in the statement.
Comcast's offer pits the biggest cable operator in the U.S. against Murdoch's Fox. However, Disney has agreed to buy a string of assets from Fox — including its current 39 percent share of Sky — making the picture more complicated. Disney CEO Bob Iger declined to comment about Comcast's proposal, according to Reuters.
Disney still views Sky as a desirable asset and shared ownership of the company is seen as less than ideal, sources familiar told David Faber.
Late last year, Comcast reportedly approached Fox and expressed an interest to acquire some of its assets. The U.S. cable operator was thought to be interested in the same set of assets that Disney eventually agreed to purchase.
The latest round of major deals comes at a time when traditional cable television networks have been losing customers to streaming services such as Amazon and Netflix.
Fox had already agreed on a deal of 18.5 billion pounds ($25.8 billion at the current exchange rate) to buy the 61 percent stake in the U.K.-based broadcasting group it does not currently own. But last month, the U.K.'s competition authority provisionally found Fox's bid for Sky would not be in the public interest.
The Competition and Markets Authority cited concerns the Murdoch Family Trust would have too much influence over public opinion and the political agenda if the deal went through. It added that spinning off or divesting Sky News, insulating Sky News from Fox's influence, or blocking the deal outright would be possible solutions. However, if Disney's acquisition of the Fox assets go through, that could lessen the Murdoch family's clout in the U.K. and possibly placate the regulator.
In an emailed statement, Sky said its independent directors were mindful of their fiduciary duties and their obligations under the U.K. takeover code, adding that shareholders are being advised to take no action as no firm offer has been made at this point.
Alex De Groote, digital and media analyst at Cenkos Securities, said Comcast's "opportunistic" bid would likely spark a "fully-blown auction."
When asked whether Comcast's offer seemed a somewhat generous improvement from Fox's, De Groote replied: "(Sky) have just won the Premier League (soccer) rights for another three years. They are performing well operationally. They're performing well in Germany and Italy. … I could see this stock price going way north of 12.50 (pounds) and counter approaches coming both from Fox and maybe even a third party."
At the start of the month, Sky won a bulk of Premier League television rights for the 2019-2022 soccer seasons. But Michael Cavanagh, chief financial officer at Comcast, said while the Premier League auction was a factor, it had not been the driving force behind the firm's offer.
When speaking about Sky News, Sky's international multimedia news organization, Comcast's Roberts said it intends to maintain Sky News' existing brand and culture.
"While Comcast does own a substantial international operation in the U.K., with more than 1,300 employees, the company has only a minimal presence in the U.K. media market. Comcast therefore does not believe that this Superior Cash Proposal should create any media plurality concerns in the U.K.," he said in a statement.
Disclosure: Comcast is the owner of NBCUniversal, parent company of CNBC and CNBC.com.