The deputy chief of the German Civil Service Federation (DBB) told the Süddeutsche Zeitung in an interview published on Friday, that if DB didn't start playing ball with its opponents it would call for an escalation to the industrial action.
The DBB is the umbrella organisation to which the GDL belongs to and manages the strike fund that finances the GDL's industrial actions.
"All previous strikes will look like child's play compared to what we have planned, " said Willi Russ.
He also added that future strikes won't be hampered by lack of funding on the unions' behalf.
On Thursday, the federal cabinet sent through a new law in collective bargaining that is intended to protect consumers from prolonged labour disputes. The law creates a legal framework for collective bargaining where an agreement cannot be reached.
But some unions are saying that it creates a hostile environment for smaller unions. The law is to take effect summer 2015.
On Friday, Deutsche Bahn is meeting with GDL and EVG in separate collective agreement negotiations. The EVG, representing more than 17,000 rail workers, said they received a "decent offer".
The GDL and EVG are asking for a raise and a shorter work week. The GDL, however, is also asking to negotiate on behalf of all unionized DB employees, swelling its members from 2,200 to nearly 20,000.
This has effectively driven a wedge between the two rail unions and forced them to negotiate separately with the rail network.
The GDL has promised no new strikes until January 11, 2015 to accommodate the busy holiday travelling season.
Meanwhile, DB has made the first step in providing free wireless internet in trains starting on December 14, but only for the first class. It previously announced that all classes would have access to free wifi as of 2016.
As a result, the price of first class tickets has increased by 2.9 percent on average.
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