The Belgium international spent 2012-13 on loan in the Bundesliga with Werder Bremen - scoring 10 goals in 33 appearances.
He returned to Chelsea in the close-season, making his debut for the club against Hull City in their first game of the season, but has featured just twice since.
Having failed to make a Premier League appearance since September, De Bruyne's Stamford Bridge future has been in doubt since he was blasted by Jose Mourinho for a lack of effort in a League Cup tie at Swindon Town in September.
The 22-year-old was forced to train with Chelsea's youth side and the Portuguese confirmed on Saturday that bids had been made for his services.
He told Wolfsburger Nachrichten: "It's not that we can confirm the deal just yet, but we are no longer so far apart with Chelsea that we can't bridge the differences."
