The Senegalese frontman has been linked with a number of Europe's top clubs, including Spurs, Arsenal and Paris St Germain. But Newcastle boss Alan Pardew has warned Ba that even if he stays on Tyneside until the end of the season, he will be sold if he does not agree a new contract without a minimum fee release clause.
The 27-year-old has a £7.5m release clause in his contract that becomes active during the transfer window, and Pardew wants Ba to renegotiate a new deal without the clause.
Pardew said in the Daily Mail: "Really and truly this window is the key, I think, because if Demba goes in this window, it will cause us a problem.
"I think he will stay, but there's a possibility he could go because of the clause that's still in force. In the summer, I won't let it run until the summer. I'll do something about it.
"We will either move Demba on or we will secure him in the summer."
The former-West Ham frontman has been in excellent form this season - he already has 11 Premier League goals - sparking interest from the likes of Tottenham, Arsenal and Liverpool.
Andre Villas-Boas and Arsene Wenger are both expected to be active during the January transfer window, but Pardew is unlikely to be willing to sell to Premier League rivals mid-way through the season.
Ba's contract clause has caused uncertainty at Newcastle during the past two transfer windows, and Pardew is thought to want to end speculation linking Ba with the likes of Arsenal and Spurs once and for all. But, while the clause stays in place, the prospect remains that a £7.5m bid from an interested party would give Ba a decision to make over his future.