Rangers made an initial bid of £250,000 for the 25-year-old hitman, but that offer was a considerable way short of Dundee’s valuation of a player who scored 25 goals last season.

Celtic have now upped the ante by making an official approach, which is likely to start a bidding war between the Glasgow giants.

Dundee, however, insist they will not be sold short and, with season ticket sales continuing at a healthy rate — 2200 have now been snapped up — are in no rush to sell their prize asset.

Jim Duffy is still on holiday and nothing is likely to be done until the Dens boss returns.

A spokesman for Dundee confirmed an approach had been made, but added Novo would only be leaving if the fee suited Dundee.

He said, “I can confirm we have an official inquiry from another SPL club for Nacho Novo.

“But there is no need for us to do anything in haste. What we would never do is name a price for the player, that would be completely foolhardy.

“We’ve an idea in our minds what Nacho’s true value is and it’s up to clubs to make realistic offers.

“But we are now two thirds of the way towards bringing in the money we need to from season tickets to meet our business plan and, as long as the fans continue to respond as they have done, there is no pressure to sell anyone for a knockdown price.”

However, with Martin O’Neill now officially entering the race for Novo — Leicester City have also been credited with an interest — it seems almost inevitable the former Raith Rovers man will be moving on.

Meanwhile, it’s believed a second Premiership club are showing an interest in keeper Julian Speroni. Crystal Palace have already tabled a £500,000 bid for the Argentinian.

Dundee United held their AGM today at Tannadice.