Comcast said in a statement that it hasn't made a final proposal, but "the work to finance the all-cash offer and make the key regulatory filings is well advanced."
Disney agreed to buy most of 21st Century Fox's assets, excluding Fox News, Fox Business, and other properties, for $52 billion.
Comcast said Wednesday it was considering an all-cash offer for most of 21st Century Fox's assets to outbid Disney's previously announced deal.
Reports earlier in May indicated that Comcast was speaking to investment banks, preparing a bid to surpass Disney's $52 billion offer. The assets Disney agreed to buy in December excluded the Fox News Channel and Fox Business Network, to avoid the regulatory scrutiny that would come with a single company owning ESPN and several other broadcast networks.
The competing offers come amid ratings declines across TV broadcast networks, as more viewers opt for cheaper streaming and on-demand content. If Disney wins over Comcast, it would beef up its entertainment slate with cable channels like FX.
Comcast's announcement escalated a bidding war that was already underway in Europe for Fox's satellite business. Comcast made a £22 billion ($30 billion) offer for the 61% stake it doesn't already own in the European pay-TV group Sky, and won government approval on Monday.
Comcast said it hasn't made a final proposal, but "the work to finance the all-cash offer and make the key regulatory filings is well advanced." Earlier reports indicated that Comcast was waiting on a US judge's ruling on AT&T's planned acquisition of Time Warner before submitting an offer for Fox.
Comcast shares fell by as much as 2% in premarket trading.