Roberts said the Sky board's withdrawal of its support for Fox's offer was "the flawless step as far as we are concerned today".
Comcast, which first outlined an offer at the same £12.50 a share price in February, said it would continue to engage with the Sky's independent directors with a view to obtaining a recommendation for its deal.
Mr Murdoch's 21st Century Fox said it was "considering its options", but "remains committed to its recommended cash offer for Sky".
"The question now is whether Fox/Disney makes a knockout bid to discourage any further Comcast offer and what it thinks this level is, without breaking the bank", analysts at Liberum Capital said in a note to clients.
Comcast also said it will give legally-binding commitments to maintain editorial independence at Sky News.
Tulchan's Andrew Grant and Tom Murray are working the Comcast bid. "We have long believed Sky is an outstanding company and a great fit with Comcast".
As a result of the higher offer, Sky said that it has withdrawn its recommendation to its shareholders of the 21st Century Fox bid, and is terminating its Co-operation Agreement with 21st Century Fox, entered on the date of the Fox offer.
Comcast Chairman and CEO Brian Roberts said Sky withdrawing its recommendation on the Fox bid was what the United States cable giant wanted to achieve by formalizing its offer on Wednesday.
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The scandal, at least for now, hasn't resulted in any significant loss in users for the California-based social media giant. Visitors take photos in front of the Facebook logo at the company's headquarters in Menlo Park, Calif., on March 28, 2018.
Not acquire any majority interest in United Kingdom newspapers for five years.
Comcast, which owns cable channels MSNBC and CNBC as well as telecoms services, has already said it believes its approach would escape concerns over media plurality because of its "minimal presence" in United Kingdom media.
The company laid out a strategy that showed it was interested in being a good corporate citizen in Britain, promising to use Sky as a platform for growth in Europe, maintaining Sky's United Kingdom headquarters and using the acquisition to "expand Comcast's worldwide footprint".
A tie-up between the two would create a business with around 52 million customers and give Comcast a platform for growth across Europe. "We look forward to receiving the necessary regulatory approvals".
The NBC and Comcast logo are displayed on top of 30 Rockefeller Plaza, formerly known as the GE building, in New York, New York, U.S. on July 1, 2015.
Sky's statement said: "At this time, the independent committee notes that both offers are subject to pre-conditions and neither offer is now capable of being put to shareholders".
On Wednesday, Sky also welcomed commitments the USA cable giant had made to address potential public-interest concerns over Sky News, its influential 24-hour news channel.