The deal has been agreed by the independent directors of both company's boards though other elements of the deal remain under discussion, and Sky has said there is "no certainty" a formal offer will be made.
The independent directors are recommending the deal to Sky shareholders, subject to final terms being reached. The deal will see Fox pay £10.75 per share to buy the 61% of Sky that Fox does not already own.
However, questions have been raised as to the independence of the agreement, since the Sky board is chaired by James Murdoch, son of Rupert Murdoch, and chief executive of Fox.
Fox already holds a 39% stake in the British broadcaster and telecommunications company. Four years ago News Corp - the name for Murdoch's empire before it was split and 21st Century Fox formed - attempted an acquisition of Sky.
However, this was thwarted by political opposition amid the phone hacking scandal at its British newspapers, leading to the closure of News of the World.
Today's (9 December) deal is still likely to spark a debate among critics of the Murdochs who argue the phone hacking scandal should still disqualify them as fit owners of Sky.
Media analyst and former newspaper editor, Paul Connew, suggested that apart from the possible political repercussions, rival media organisations could attempt to derail the deal.
"Before the phone hacking scandal scuppered the Murdochs' bid in 2011, an alliance of most major newspaper companies, including the Mail, Mirror and Telegraph groups and the BBC launched a legal challenge to the plan," Connew told The Drum.
"It will be interesting to see whether they decide to revive their previous challenges to the deal on competition and concentration of media ownership grounds. "
The bid has been long rumoured since James Murdoch returned as Sky chairman in January this year, an indication that the Murdoch empire might revive its ambition to fully take over the broadcaster.
The announcement of the bid to the Stock Exchange saw Sky shares jump nearly 30% to £10.26.