Wolfsburg admit Manchester City-target Kevin De Bruyne is feeling the strain of the constant transfer speculation surrounding his future amidst a UK report he will join City before the weekend.

Although he publicly pledged his future to Wolfsburg on Monday, 'The Sun' claim De Bruyne is set to become a City player in the next 48 hours in a deal worth a £50 million (69.9m euros, $78.1m) after the Premier League giants raised their offer.

Wolves, last season's German league runners-up, are at Cologne in the Bundesliga on Saturday after beating Eintracht Frankfurt 2-1 in their opening match of the new season last Sunday, but the City speculation is taking a toll on De Bruyne.

"Kevin is a bit tired, because there is so much going on," Wolfsburg's coach Dieter Hecking told German daily Bild after the Belgian international trained alone on Wednesday.

"It's a situation which is still bothering him and we're trying to keep him in the best condition."

At an awards ceremony on Monday, the 24-year-old said he is "sure" he will stay at Wolfsburg this season and replied "of course" when asked if he will line-up for the defending champions against Bayern Munich in the German Cup at the end of October.

But Wolfsburg face an anxious wait until the transfer window closes on August 31 and director of sport Klaus Allofs has said their sole objective is to keep De Bruyne on their books.

The Belgian was named Germany's player of the season in 2014/15 and has been outstanding for Wolfsburg since signing from Chelsea in January 2014.