In the wage dispute at Deutsche Bahn, the train drivers' union GDL is increasing the pressure on the group.
On Thursday she asked for a "negotiable offer" by the beginning of next week.
Otherwise the next strike will be prepared from Monday, the union announced.
Chairman Claus Weselsky did not comment on possible dates for a new strike.
"We gave Deutsche Bahn (DB) time to think after the last strike, but it seems to me that the DB is taking a bit of time to think about it," criticized Weselsky.
The train is apparently playing for time, but that can no longer be an option.
The GDL has already struck three times in the current collective bargaining round for its goals, most recently in passenger transport for five days.
The collective bargaining dispute is about higher pay and better working conditions for employees.
The union also wants to expand its sphere of influence in the group.
Deutsche Bahn now wants to present the GDL train drivers' union with a "new and improved" offer by the weekend. The German press agency learned this on Thursday evening from the environment of the two collective bargaining parties. The declared aim is to find solutions with the union at the negotiating table as soon as possible.