Tottenham have accepted a bid from Spartak Moscow for defender Davinson Sanchez.
The Russian club have offered around £12m for Sanchez, who is in the final year of his contract.
However, Sky Sports News have reported that he is reluctant to make the move.
It comes as Tottenham boss Ange Postecoglou looks to revamp his defensive options.
Postecoglou is hoping to sign at least one centre-back before the start of the new Premier League season.
Spurs hoped to have added defensive reinforcements to their squad by now, but the search is continuing.
Speaking at a press conference ahead of the pre-season friendly against Lion City Sailors in Singapore, Postecoglou said: “We’re looking to bring in at least one.”
He added: “No frustration – it’s just the football world. I’ve been around long enough to know how it works.
“I wish it could be like my wife and Amazon, where we get a delivery every day. But no frustration.”
There continues to be speculation over the future of Tottenham and England striker Harry Kane, who is wanted by German giants Bayern Munich.
But Postecoglou said: “There’s no news on Harry Kane. At the moment there’s nothing that’s changed from a couple of days ago.”
The Telegraph reported this week that Tottenham owner Joe Lewis has made it clear to Daniel Levy that he does not want to risk Kane, who has a year remaining on his contract, leaving on a free transfer next year.
Chairman Levy, it is claimed, has therefore been told he must sell Kane if he cannot persuade him to sign a new deal.
The Daily Mirror, meanwhile, say that has put Manchester United, who have also been linked with Kane, on alert.