By Manchester correspondent Alex Stevens

Manchester United are ready to join the £40million race to sign John Stones, Football Insider sources understand.

The Premier League’s highest revenue-generating club are closely monitoring the form of the England defender.

Stones was outstanding for England in their 2-0 win over France on Tuesday night and has delivered a series of polished displays for Everton since failing to push through a move to Chelsea in the summer.

The Merseysiders rejected three bids for Stones from the Premier League champions last summer – the final one was of £30million – and refused to sell even when the 21-year-old submitted a transfer request late in the window.

A source has told Football Insider that Everton are keen to open talks with Stones on an extension to his contract, which runs until 2019, as a reward for his impressive progress.

Chelsea are ready to move again for the centre-back in the January transfer window as they attempt to strengthen a squad that has had a wretched start to the season.

The Londoners have identified Stones as the long-term successor to Terry and remain determined to make him the most expensive English defender in history. The current record is the £30 million that Manchester United paid Leeds United for Rio Ferdinand in 2002.

Rock solid: Stones delivered another polished display as he shone for England on Tuesday

Rock solid: Stones delivered another polished display as he shone for England on Tuesday

But the Blues face competition from United and neighbours Manchester City.

Everton manager Roberto Martinez has insisted that the England international will not be sold and that his future will be at Goodison Park.

However, Chelsea and United have been encouraged by Stones’ private stance that he is attracted by the idea of moving to a Champions League calibre club.