Comcast announced an offer worth $65 billion for the bulk of 21st Century Fox’s businesses on Wednesday, setting up a showdown with the Walt Disney Co. for Rupert Murdoch’s media empire.

The all-cash bid by Comcast came a day after a federal judge approved a merger between AT&T and Time Warner. That deal had been challenged by the Justice Department, and Comcast executives had awaited the judge’s decision before mounting their bid for 21st Century Fox.

In December, Disney struck a $52.4 billion, all-stock deal for Fox’s assets. Comcast, whose roughly $60 billion offer for the Fox assets was rebuffed last year, is now including contractual assurances such as a reverse breakup fee — worth about $2.5 billion — in the event a transaction is blocked by the government.

At $35 a share, Comcast’s new offer is about 19 percent higher than Disney’s proposal, according to its statement.

Murdoch and his company’s board had rejected Comcast’s earlier offer partly on concerns the government would block the deal. But the AT&T-Time Warner decision also allayed many concerns that a Comcast takeover of 21st Century Fox’s businesses would be blocked by regulators.

Brian L. Roberts, the head of Comcast, needed to move quickly. Fox shareholders are scheduled to vote on the Disney deal on July 10, but that date will be moved back if Murdoch and the Fox board decide to support Comcast’s offer. Disney would then have five days to respond with a counter bid.

The businesses Murdoch has agreed to sell include the 20th Century Fox film and TV studios, almost two dozen regional sports networks like the New York Yankees’ YES channel, a lineup of cable networks that includes FX and a 30 percent ownership stake in the streaming service Hulu.

But the key attractions for Comcast are Fox’s broad international assets, which include its 39 percent stake in the European pay TV operator Sky and its control of Star, one of India’s largest media companies, which reaches 700 million people every month, according to the company.

Murdoch’s overseas business accounts for 27 percent of annual sales, about $7.8 billion. Comcast, whose cable business is strictly a domestic operation, draws in only 9 percent of its revenue from foreign agreements, largely through its NBCUniversal division.