Gabriel Heinze, the disaffected Manchester United defender, has been offered to Real Madrid and Barcelona at a discounted fee in a last-ditch attempt to prevent the Argentinian from pursuing a move to Liverpool.

A Premier League arbitration panel meets tomorrow to rule on Heinze’s future, but in a new twist to an increasingly malevolent saga, it has emerged that Spain’s leading two clubs have been asked if they would like to sign the player for less than the £6.8m United named as his “release price” in a letter to Heinze’s agent.

The development may be a further signal of how desperate United are not to sell him to Liverpool. Heinze says the letter gives him permission to join any club willing to pay £6.8m, as Liverpool are. United insist it was always made clear to Heinze that he would not be allowed to move to one of their main Premier League rivals. Lyon, the French club, have expressed a willingness to meet the £6.8m valuation and there is also interest from Juventus in Italy but Anfield is Heinze’s favoured destination.

It is thought to be unlikely that Real Madrid or Barcelona will offer a way out of the mess. Despite the opportunity of acquiring a top international at a reduced price, Real have other transfer priorities. The Spanish champions are still pursuing Chelsea’s Arjen Robben and Daniel Alves of Sevilla, who would each cost in the region of £20m. Barcelona are believed to be happy with their options at left-back, having recently signed Eric Abidal.

Heinze has given no sign he will back down over his wish to become the first player to move directly from United to Liverpool since Phil Chisnall in 1964. It is understood, indeed, that the defender is prepared to take his case to Fifa should the Premier League rule against him.

At the centre of the dispute is the letter, given to Heinze’s agent, Roberto Rodriguez, and signed by United’s chief executive, David Gill. United told Rodriguez that their valuation of the player was £6.8m and that he could negotiate with interested clubs. No exceptions were named but Gill says Rodriguez was made aware at a subsequent meeting that offers from Liverpool, Chelsea or Arsenal would not be considered.

A measure of the saga’s bitter nature is that it is believed a tape recording was made of a conversation between Gill and Rodriguez to be used as evidence in the event of the case ending up in court.

Heinze is in full training with United but Sir Alex Ferguson indicated he will not be considered for selection today. Ferguson and Gill have stated it is still possible for Heinze to remain at Old Trafford and play for United, despite him seeking a move to his club’s fiercest rivals. Their anger is directed towards Rodriguez, whose conduct a United source branded “ungrateful”.

In legal terms, the dispute is a contract issue between Heinze and United, and Gill has said he has “no issue with what Liverpool have done”. The Anfield club are convinced that Heinze will win the fight and Rafael Benitez has kept a place open for the Argentinian in his squad.