Comcast is preparing to announce bid for Fox on Wednesday if AT&T-Time Warner is approved, sources say

• Comcast will formalize its all-cash bid for Fox's assets on Wednesday if AT&T's bid for Time Warner is approved, sources say.
• Comcast executives think Disney's stock will fall if AT&T's acquisition of Time Warner is approved because Disney will have to prepare for a bidding war.
• Comcast has already acknowledged it is in the advanced stages of preparing an all-cash rival bid.

Comcast will formalize its all-cash offer to acquire most of Twenty-First Century Fox on Wednesday if U.S. District Court Judge Richard Leon approves AT&T's deal for Time Warner on Tuesday, according to people familiar with matter.

Comcast, which owns CNBC parent company NBCUniversal, has already publicly acknowledged its plans to compete with Disney on an acquisition of Fox assets, including Fox's movie studio, the Nat Geo and FX networks, regional sports channels, and stakes in Hulu, Star India and Sky PLC. CNBC reported last month that Comcast was preparing to raise $60 billion in a deal for Fox while simultaneously pursuing a $31 billion offer for the 61 percent of Sky that Fox doesn't already own.

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Announcing an offer on Wednesday, rather than Tuesday afternoon, will allow Comcast's lawyers to look through the details of Leon's decision, the people said. Comcast advisors and executives believe Comcast's rival bid for Fox will put pressure on Disney's shares, as Disney may to have raise its outstanding $52 billion all-stock offer. Waiting until Wednesday, if Disney shares fall, could also accentuate the difference in value between Comcast's bid and Disney's offer, one of the people said.

Disney's hasn't said if it will improve its bid for Fox. A Comcast spokeswoman declined to comment.

Disclosure: Comcast, which owns NBCUniversal, parent company of CNBC and CNBC.com, is a co-owner of Hulu.