Executives at Comcast believe the plan will be completed in about a year. Their expectation is that Comcast will be better placed for growth after the spinoff.
They are understood to believe the new company will be in a position to buy other cable TV networks that could potentially go up for sale in the future.
The new firm will have the chairman of NBCUniversal’s media group, Mark Lazarus, as its chief executive.
Comcast’s president, Michael Cavanagh, first hinted at the plan during a call with investors last month.
At the time, Mr Cavanagh said he was exploring a strategy that could create “a new well-capitalised company owned by our shareholders and comprised of our strong portfolio of cable networks”.
Comcast took control of NBCUniversal in 2011 before the rise of streaming. At the time, its cable networks were seen as some of its most attractive businesses.
But a growing number of cable TV viewers have been cancelling their subscriptions and moving on to streaming platforms.
Comcast is the first major media company to make such a move.
Earlier this year, Warner Bros and Paramount Global cut billions of dollars from the valuation of their cable TV networks.
Walt Disney has also considered spinning off its cable networks but ended up scrapping the plan.