Newcastle have rejected a £1.75million bid from Anderlecht for Matz Sels.
The Toon keeper, 26, was expected to seal a permanent move to the Belgian club, where he spent last season on loan.
But Newcastle want at least another £500,000 from Anderlecht, who are refusing to up their offer at all.That has thrown the whole deal into major doubt and means the Magpies could be left with four senior keepers on their wage bill.
Martin Dubravka joined Newcastle on a permanent deal last month after a successful loan from Sparta Prague.
He was loaned to Anderlecht for the 2017/18 season and was a success back in Belgium.
The 26-year-old kept eight clean sheets for Anderlecht.