Borussia Dortmund are leading the chase to sign Manchester United midfielder Henrikh Mkhitaryan, who is expected to exit Old Trafford after falling out of favour with manager Jose Mourinho.

Mourinho has hinted that he could let Mkhitaryan leave the club in January after growing frustrated with his poor form.

The Independent says Dortmund have shown the strongest interest in signing the Armenia international, whom they sold to United for £30m ($40m) in July 2016.

The 28-year-old has not started a game for United since 5 November and has been left out of the matchday squad for the club's last five matches.

United will demand a transfer fee of £35m from any club wanting to sign Mkhitaryan, according to the Daily Mail.

Mourinho has identified Chelsea midfielder Willian, Arsenal playmaker Mesut Ozil and Bordeaux's Malcom as potential replacements should Mkhitaryan be sold.

"I think, for the right price [I would sell unhappy players]," the Portuguese coach was quoted as saying by FourFourTwo before United's trip to West Brom.

"That's my approach as a manager, in cases where the club advises me. Every player has a price.

Henrikh Mkhitaryan
Armenia midfielder Henrikh Mkhitaryan has fallen out of favour at Manchester United Getty

"If a player is not happy, if a player brings with him the request with the number that we consider a good number for us, like it happened with Memphis [Depay] and Morgan [Schneiderlin], I would never say no."

Sources close to United told ESPN that the relationship between Mourinho and Mkhitaryan had broken down following a row between the two during a video analysis session at the club's Carrington training ground last month.

The Armenia midfielder was reportedly unhappy at Mourinho for singling him out for criticism over his defensive work rate in front of the rest of the first-team squad.

Inter Milan have also been linked with a move for Mkhitaryan, with the Serie A club willing to offer Portuguese midfielder Joao Mario in exchange to make a deal happen.