Under the terms of the bid, Sky shareholders would receive £12.50 in cash for each share, with the deal structured as a tender offer with a 50% plus one share acceptance condition
The US company's bid challenges bids made by 21 Century Fox and Disney.
Sky is the UK's biggest pay-TV company.
Merrill Lynch Pierce Fenner & Smith and Wells Fargo Securities have acted as lead arrangers on the term loan and bridge financings related to Comcast's offer.