The new company, created by the $44 billion purchase, would be by far the largest cable provider in the nation with over 33 million subscribers, and is certain to face a tough review from the Federal Communications Commission.
(Read more: Comcast, Charter discuss possible deal on TWC)
The agreement comes more than eight months after Charter Communications and Liberty Media made their first foray to try and negotiate a deal to acquire Time Warner Cable and follows months of conversations between Time Warner Cable and Comcast about the prospect of an acquisition of the company.
Charter's offer of roughly $133 a share in cash and stock has been rejected by Time Warner Cable as it held out for a price of $160, which it has said is reflective of where an asset of its size and scope should trade in a deal.
While there are no caps on the ownership of cable subs, Comcast had been thought to be lukewarm to a deal to buy all of Time Warner Cable due to its concern about being subjected to an onerous consent decree from the FCC similar to the one it signed upon acquiring NBC Universal.
(Read more: Apple, Time Warner Cable in Apple TV talks: Report)
Comcast will indicate a willingness to divest 3 million subs from the combined company, according to sources familiar with the situation.
Comcast, which is widely considered under-leveraged in the cable industry, will nonetheless use no cash in the acquisition, which is expected to be officially announced Thursday morning U.S. time.
(Disclosure: Comcast is the owner of NBCUniversal, the parent company of CNBC and CNBC.com.)