Manchester United and City are reportedly locked in battle for centre-back Marc Bartra as well as facing competition from around Europe.
The outcast Spaniard is in search of more minutes ahead of the World Cup after falling down the ranks at the Bundesliga giants.
The Manchester clubs have targeted the former Barca player according to Spanish outlet Marca.
The 27-year-old progressed through the ranks at Barcelona before being sold to Dortmund in June 2016.
Bartra has two-and-a-half years left on his contract with the German side but after seeing his playing time rapidly decline with the arrival of new boss Peter Stoger the defender is set to move on.
The Spain international can also play on the right – offering versatility across the back line – and making him a more attractive option for Pep Guardiola.
Though a move to the Etihad this winter could be doubtful after central defender Aymeric Laporte passed his medical with the club over the weekend.
Jose Mourinho’s squad is rather full on the back line with Phil Jones, Eric Bailly, Chris Smalling, Marcos Rojo and Victor Lindelof at hand.
But United may be in need of extra reinforcements given the club’s notorious fitness issues in that area.
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Juventus and Real Betis are also reportedly interested in making a move with Dortmund open to offers.
Bartra has played 51 games for the Bundesliga outfit but has moved from a starter to rarely making appearances in his second season with the club.