This time, a bid would include protections such as a reverse termination fee, the sources told CNBC.
CNBC reported Monday that Comcast was preparing a $60 billion all-cash bid that would top Walt Disney's deal to acquire the studio and production assets of Fox if the government approves AT&T's acquisition of Time Warner.
Comcast could take on significant debt in a deal, sources told CNBC on Tuesday, up to $100 billion.
But the sources also said Comcast CEO Brian Roberts and Disney CEO Bob Iger aren't communicating about resolving this bidding battle.
Disclosure: Comcast is the owner of NBCUniversal, parent company of CNBC and CNBC.com.