"As of today, I cannot imagine that we'll reach a reasonable agreement in the night from Wednesday to Thursday," Stefan Wolf, head of regional employers' association Suedwestmetall, said.

After that the two sides could either strike a deal over the weekend or trade union IG Metall could opt to call for 24 hour strikes next week, he added.

Spurred on by the fastest economic growth in six years and record low unemployment, IG Metall is demanding 6 percent more pay for 3.9 million metals and engineering workers across Germany.

A fourth round begins in the southwestern state of Baden-Wuerttemberg, home to Mercedes-Benz maker Daimler (>> Daimler) and sports car brand Porsche (>> Volkswagen), on Wednesday.

Any deal in Baden-Wuerttemberg would typically be applied in other states as well.

A big sticking point in the talks is a union demand that workers should have the right to reduce their weekly hours to 28 from 35 to care for children or elderly or sick relatives, and return to full-time employment after two years.

Employers have so far offered a pay rise of 2 percent plus a one-off 200-euro (176.33 pounds) payment but have rejected demands for a shorter work week unless employers are allowed to increase hours temporarily as well.

(Reporting by Ilona Wissenbach; Writing by Maria Sheahan; Editing by Christoph Steitz)

Stocks treated in this article : Daimler, Volkswagen