George Boateng's agent has told Celtic they must move quickly if they are to sign the midfielder from Middlesbrough.
According to the Daily Record the 32-year-old visited the Bhoys' training complex on Thursday, but his representative Barry Silkman says Gordon Strachan's men are yet to meet Boro's valuation.
And with Hull and another as yet unnamed English Premier League side having already had bids accepted, Celtic have been told they must act.
Silkman told the Daily Record: "I've spoken to two Premier League clubs after Middlesbrough accepted their offers.
"Those clubs want to do a deal this week so things will move quickly now.
"At the moment Celtic haven't met Middlesbrough's valuation.
"It is hypothetical to discuss a move to Scotland because you need to look at the clubs that have come up with the goods so far.
"Things are dictated by what Celtic do. If Middlesbrough get an offer from then we'll talk, but right now he's staying in England."