Chelsea have made a €50 million ($57.1m) follow-up offer for Jamie Gittens as they step up their pursuit of the Borussia Dortmund winger, sources have told ESPN.

The west London club are keen to strengthen their attacking options this summer and have already had an offer around €35.5m rejected by the Bundesliga side.

The 20-year-old is keen on a move to Stamford Bridge and Chelsea need to move quickly to ensure he will be eligible to compete in the Club World Cup. The deadline for registration is Tuesday.

Gittens has made 48 appearances for Dortmund this season in all competitions, scoring 12 goals and registering five assists.

He is a former Manchester City youth team player and they hold a clause guaranteeing them 10% of his next transfer fee as part of the deal which took him to Germany in 2020.