The France U21 defender emerged as a target for Alan Pardew earlier this month and has also been linked with Roma.
Haidara's priority is to join a Premier League club, and he could now get his wish after Nancy accepted an undisclosed offer.
He said recently: "Newcastle do appeal to me, but everyone has to agree.
"I would be very happy to play there. My preference is England. It is the league which attracts me the most and would suit my game the best."
Haidara is the third French defender pursued by Newcastle this transfer window.
Mathieu Debuchy has already arrived and a bid for Montpellier's Mapou Yanga-Mbiwa has been agreed.