Dortmund announced on Thursday that they had rejected a bid from Barcelona for Dembele - reported to be worth around €100 million - and suspended the France forward after he failed to attend training.
He said: 'Our focus now is on preparation for the Bundesliga opening match in Wolfsburg.
Dembele missed Dortmund's DFB-Pokal match against Rielasingen-Arlen as Maximilian Philipp and Andre Schurrle played on the wings, with Pierre-Emerick Aubameyang netting a hat-trick after Marc Bartra opened the scoring.
Speculation that a move to Barcelona was imminent soon mounted before BVB issued a statement saying a bid had been lodged by the Catalan giants but it did not meet their valuation for a player they signed from Rennes for €15m a year ago.More news: Mattis says United States wants diplomatic solution for N. Korea
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The France global was one of Dortmund's best players last season as they finished third in the Bundesliga, scoring six goals and contributing a further 12 assists in 32 league appearances.
"Ousmane Dembele has, of course, the opportunity to train individually, away from the squad".
His unauthorised absence came after Barca had a bid rejected for the France worldwide, who has been earmarked by the Liga powerhouse to replace Neymar following the Brazil star's world-record €222million transfer to Paris Saint-Germain this month.
Dembele joined Dortmund a little over 12 months ago from Rennes on a five-year contract and scored 10 times in 49 appearances in all competitions last season.