BERLIN, Aug 20 (Reuters) - Germany"s GDL train drivers" union on Friday said its members would go on strike over a wage dispute from Aug. 21 until Aug. 25, its second action within weeks. The strike would start at Deutsche Bahn"s cargo business on Saturday at 5 p.m. (1500 GMT) and would affect passengers from 2 a.m. (0000 GMT) on Monday, GDL chief Claus Weselsky said. The train drivers, who went on strike from Aug. 10 until Aug. 13, would not hesitate to start holding strikes at busy weekends in future if Deutsche Bahn did not come up with a new proposal that satisfied their demands, Weselsky said. GDL is demanding a wage increase of around 3.2% and a one-time coronavirus allowance of 600 euros ($700). Deutsche Bahn said earlier this month that its offer was very close to GDL"s demands. "We have once again taken into consideration the coming weekend," said Weselsky. "We will not be able to guarantee this in future." ($1 = 0.8567 euros) Reporting by Markus Wacket, writing by Kirsti Knolle; Editing by Joseph Nasr and Alex Richardson Our Standards: The Thomson Reuters Trust Principles.