German train drivers started a four-day strike against state-owned rail operator Deutsche Bahn on Wednesday that threatens to harm the economy and prompted a rare intervention from Chancellor Angela Merkel who called for a mediator. Deutsche Bahn’s freight train drivers walked out on Wednesday and passenger trains will be hit from early Thursday. They will stay out until Monday morning, making it the longest strike in the post-war history of the German railway. In a last minute attempt to ward off the strike that is also threatening to disrupt celebrations this weekend marking the 25th anniversary of the Berlin Wall’s fall, Deutsche Bahn urged the GDL train drivers’ union, with its 20,000 members, to accept mediation talks and abandon the strike over power and pay that will disrupt travel for millions. But GDL leader Claus Weselsky, who has been pilloried in the German media for leading his small union into a sixth strike in two months, rejected the renewed mediation offer. Mass selling daily Bild urged its readers to personally call the union leader with their views and published his phone number. Merkel, who rarely comments on industrial disputes, urged the train drivers to act with restraint, saying that mediation between the GDL union and Deutsche Bahn should be considered. “I can only appeal to their sense of responsibility to find solutions which do the least possible damage to us as a country - while maintaining the right to strike,” Merkel told reporters. The Cologne Institute for Economic Research estimates that a train strike of more than three days could cost the economy up to 100 million euros ($126 million) a day if firms have to halt assembly lines because of supply shortages. Nearly one-fifth of freight traffic in Europe’s biggest economy is transported by rail. FEAR OF PRODUCTION LOSSES Car makers, one of Germany’s leading export industries, have tried to redirect parts of their logistics away from railways to roads, a spokesman of the association for freight, logistics and disposal said. But the number of lorries in Germany was limited. Volkswagen, BMW and Audi said their goal was to prevent any stoppages in production. Deutsche Bahn has vowed to maintain around half of freight traffic despite the strike, with priority given to power plants, steel works, chemical plants and car factories. For passenger traffic, Deutsche Bahn aims to maintain a third of all train services. The network carries 5.5 million passengers and more than 620,000 tonnes of freight each day. The walkout is the latest in a series of GDL strikes. In mid-October the union staged a 60-hour strike over a weekend, halting two-thirds of long-distance trains and leaving millions of passengers stranded at the start of school holidays. The GDL, which represents just 20,000 of the railways’ 196,000 workers, argues that the company is to blame for the crisis by denying the union the right to negotiate on behalf of 17,000 train stewards. It also seeks a 5 percent pay rise for drivers and a shorter working week of 37 hours, down from 39. Strikes in Germany are rare, with employers and larger unions usually able to resolve their differences at the negotiating table. GDL’s attempt to raise its influence by negotiating for other railway workers is a move that companies and politicians have criticized and want to curb. The government is working on a new law to limit the power of smaller unions like the GDL.