Union IG Metall announced 24-hour “warning strikes” by workers at more than 250 firms this week, after talks with employers over their demands for a six-percent pay rise and the option to go part-time for up to two years fell through Saturday.

Some walkouts, including at industrial conglomerate ThyssenKrupp and auto
supplier ZF Friedrichshafen, will begin as early as Tuesday evening.

“No one wants a big industrial dispute,” union leader Joerg Hoffmann told Berlin's Tagesspiegel newspaper.

He said the stubbornness of management left “no way out” but strikes in the union's battle on behalf of almost four million workers.

“The business environment is fantastic, companies' earnings are extremely good, and they're making us an offer (on pay) that doesn't even make up for inflation over the 27 months it would run,” Hoffmann said.

It is the first time IG Metall has made use of the one-day strikes.

Unlike in shorter previous walkouts, workers will be compensated from union coffers for their loss of pay from the 24-hour industrial action.

And beyond the warning strikes, IG Metall also warned it is prepared for an open-ended strike across the metalworking sector — a pillar of the German economy — from next week.

Aside from pay hikes, a major sticking point in talks has been IG Metall's insistence that workers should have the option to switch to 28-hour weeks at will for up to two years, with a guarantee of returning to full-time work afterwards.

The employee representatives are also pushing for firms to top up the pay packets of workers who take that option to care for children or other dependents, or who use it to seek relief from the toughest jobs.

Bosses have insisted that such a move would be discriminatory towards workers who have gone part-time under less generous terms, and possibly even illegal.

“IG Metall's refusal (to negotiate), their ultimatum and their breaking off talks show they just want to strike for the sake of it,” Bertram Brossardt, director of Bavarian metalworking sector employers' association VBM, said in a statement.

In a separate industrial dispute, IG Metall announced workers at Volkswagen would walk out Thursday after pay and conditions talks with the world's largest carmaker stalled.