Emboldened by robust German economic growth and record low joblessness, the powerful IG Metall union is demanding 6 percent more pay for 3.9 million metals and engineering workers.

It has also embarked on its first major campaign for shorter working hours in more than three decades, demanding that workers gain the right to reduce their weekly hours to 28 from 35 to care for children or elderly or sick relatives and then return to full-time employment after two years.

Employers have so far offered 2 percent plus a one-off 200- euro ($239) payment in the first quarter. They have rejected demands for a shorter working week unless hours could be increased temporarily as well so as not to put output at risk.

"Mid-sized companies like ours are already suffering from a scarcity of skilled workers, which would just become worse" under IG Metall's proposal, Stefan Wolf, the chief executive of car parts maker ElringKlinger and head of regional employers' association Suedwestmetall, told Reuters.

But unions such as IG Metall say it is time for workers to get a bigger share of corporate profits and for companies to step up and take social responsibility with the economy growing at its fastest pace for six years.

"We expect employers to take a big step toward us," Roman Zitzelsberger, head of IG Metall in the southwestern state of Baden-Wuerttemberg, said ahead of talks on Thursday.

During those talks, the two sides agreed to set up a group of experts to look into the thorny topic of working hours, before more talks on Jan. 24 when negotiators will make a serious attempt to resolve the dispute, Zitzelsberger said.

"The warning strikes continue. There is no reason for us to take the foot off the gas," he said.

Employers representative Wolf said the talks made some progress: "We were miles apart. Today we have moved a little bit towards each other."

More than 76,000 workers at hundreds of metals and engineering companies took part in warning strikes on Thursday to support IG Metall's wage claim, and the union has announced further walkouts for Friday.

Such industrial action is common in Germany before sector-wide pay negotiations, and similar walkouts took place in 2016 and 2015.

But Germany's biggest trade union has threatened to call for 24-hour walkouts if talks fail to make progress, harking back to seven weeks of strikes in 1984 that helped push through a shortening of the work week to 35 hours from 40 hours.

An Emnid opinion poll conducted for N24 television showed that 47 percent of Germans think the IG Metall demands are appropriate, while a third sees them as too high. However, 65 percent said they would not cut their working hours.

Negotiations for workers in Bavaria are due to resume on Jan. 15 and in North Rhine-Westphalia on Jan. 18.

($1 = 0.8365 euros)

(Additional reporting by Michael Nienaber; Writing by Maria Sheahan and Emma Thomasson; Editing by Mark Heinrich)

By Ilona Wissenbach