The Blues agreed a fee with Newcastle for Ba after making an official bid on Wednesday.
Ba has a release clause, understood to be Â£7.5m, which was triggered by the European champions.
A statement on Newcastleâ€™s website on Wednesday read: â€œNewcastle United can confirm that Chelsea Football Club has made an official offer for Demba Ba which has triggered the release clause in the playerâ€™s contract. The club has given the player permission to speak to Chelsea and therefore he will not be included in the squad for tonightâ€™s (Wednesdayâ€™s) game against Everton.â€
As at 9pm on Wednesday, the London club had finalised the discussion on personal terms with the player.
Preliminary discussions between representatives of the player and Chelsea had earlier broken up with the deal on the table nowhere near the Senegal internationalâ€™s expectations. Baâ€™s representatives indicated that the striker did not expect to end up in west London come the end of the January transfer window following the failed talks.
Manager Rafael Benitez said on Wednesday, â€œYou can always improve things, especially when you have injuries, and we lose two players to the Africa Cup of Nations. Obviously we need bodies but I am really pleased with the squad.â€
While the initial fee of Â£7.5m for a player with Baâ€™s track record, including 13 league goals this season, appears a bargain, the true cost of the deal could be much more. The Independent revealed that the total could be closer to Â£30m once agent fees of Â£5m and a four-year deal worth Â£80,000 a week are factored in.