Luka Modric would be open to joining Manchester United if Sir Alex Ferguson starts a bidding war with Chelsea by following the west London club in making an official offer for the Tottenham Hotspur midfielder.

After Chelsea had an initial £22m offer rejected, United are considering their options before deciding when to enter the market for a player openly admired by Ferguson, who claims he is the best footballer in England. Manchester City, the Premier League's richest club, also retain an interest and if their billionaire owner, Sheikh Mansour, enters the auction to land Modric then Spurs can expect his price to rise beyond £35m.

While Tottenham maintain that Modric is not for sale Nikky Vuksan, Modric's representative, said the Croatian would consider an offer from United if the north London club allowed him to do so. "Exactly. If that was the Spurs position then we would be happy to sit with the club and discuss for the future," Vuksan said, before being careful to emphasise Modric is not agitating for a move.

"He's happy at Spurs. Any offer that comes [in] for him, it's up to the decision of Tottenham Hotspur if they want to reject it or accept it. We have a great partnership with Tottenham and there's not been [any] activity on our behalf that we would do on our own.

"Everything is in coordination with Spurs, and it's all up to the chairman, Daniel Levy, to decide. [Luka's] under contract, he's happy there [and] he's willing to try to win the Premiership with Spurs and play Champions League [the] next season."

Yet despite that, Vuksan conceded that Modric wants to play in the Champions League each season, a prospect not on offer for him from Tottenham in the next campaign. "Of course. He loves the Champions League experience, it was a great honour for Sir Alex to say something like this and he uses it only as a motivation to continue on such a level," he said.

Asked how Modric reacted when he was told of the bid from Chelsea, Vuksan said: "I'm sorry it's inappropriate for me to say what he thinks about it. Obviously he respects the decision of the club [to turn the offer down]."

Pressed if Modric would prefer a move to Chelsea, United, City, or even Arsenal, Vuksan added: "This is a constant question and I'm sorry I really can't comment."

Regarding what comprises a realistic valuation for Modric, Vuksan said it would not be unexpected if an offer of up to £40m was eventually made for him. "Of course, I don't think it would be [to] anybody's surprise. If you ask me, Modric is one of the best and one of the probably most expensive players in the world," he said of a player who is only 25 and so is yet to reach his peak. "He's going to keep improving and get better and better."

United, meanwhile, have turned their interest in Raphaël Varane into a formal bid, offering Lens £9.2m for a teenager who fits into their policy of recruiting potential stars of the future.

Lens have provisionally accepted United's offer, though the matter is complicated. Varane has begun his Baccalaureate exams and may delay his decision until they are finished, while his excitement about moving to Old Trafford is tempered by reservations that he will be joining a club which has an established central defensive partnership in Rio Ferdinand and Nemanja Vidic, plus Phil Jones, Chris Smalling and Jonny Evans in reserve.

Varane is keen to arrange a loan in his first season, possibly meaning he will stay in France, and if that is not possible with United he must decide whether he would be better off signing for a team where he would get more games.