Manchester United and Ander Herrera are facing a race against time to find an agreement to keep the midfielder at Old Trafford beyond the end of the season, sources have told ESPN FC.

Both parties are keen to agree a new contract that would see the Spain international stay at United but, according to sources, there is still a significant gap to be bridged before a deal is sealed.

Sources have told ESPN FC that Paris Saint-Germain, Arsenal, Juventus, Inter Milan and Barcelona are among the clubs ready to sign the 29-year-old on a free transfer if fresh terms are not agreed.

If the stand-off continues, he will officially become a free agent on June 30.

Herrera would like to remain at United but so far the club, who also want him to stay, have refused to meet his demands and a compromise is yet to be found.

There is a willingness of both sides to come to an agreement but there is also an acknowledgement that the clock is ticking and Herrera may soon be forced to seriously consider other options -- especially with some of Europe's biggest clubs circling.

Talks with Juan Mata are also ongoing. The 30-year-old will also be available on a free transfer in June if a new contract is not agreed in the next three months.

Herrera is closing in on 200 games for United since arriving from Athletic Bilbao in a £29 million deal in 2014. He was named player of year in 2017 and has played a key role in the revival under Ole Gunnar Solskjaer since the Norwegian's appointment as caretaker manager in December.

United have agreed new contracts with Luke Shaw, Anthony Martial and Ashley Young this season and negotiations are continuing with David De Gea and Marcus Rashford.