Chelsea have made a £12.8m offer for Stuttgart centre-back Antonio Rudiger, Stuttgarter Nachrichten has revealed.
Rumours that the Blues were ready to make a move for the 22-year-old emerged last month when Bild reported that the player is desperate to leave the German side to join Jose Mourinho at Chelsea.
Reports in England also claim that rivals Arsenal might make an approach after the German made it clear that he is an admirer of the Gunners and their style of play.
But Chelsea continue to be strong favourites to land the 22-year-old.
"I have always dreamed of the Premier League," Rudiger told Bild last year.
"I have been following Arsenal since the days of [Thierry] Henry and [Dennis] Bergkamp.
"I watch videos of Arsenal all the time on YouTube and I often wear the current Alexis Sanchez shirt.
"My heart beats for Arsenal."