(Corrects to remove Valmet Corp from list of owners in paragraph 3)
* Jobs may go to Poland or be cut over time -IG Metall
* Related cuts may push layoffs over 900 -IG Metall
* Valmet couldn't be reached for comment
BERLIN, June 2 (Reuters) - Finnish auto Valmet Automotive plans to cut 300 jobs in Germany because of dwindling demand for convertible cars, German union IG Metall said on Monday.
The maker of roof systems will eliminate all production jobs and some white-collar positions at a plant employing 400 people in Osnabrueck, western Germany, IG Metall's regional director Stephan Soldanski said.
It is owned by Metso, the Finnish state and private equity fund Pontos. It previously was a subsidiary of Metso.
Valmet will either transfer jobs immediately to low-wage Poland or gradually phase out the positions through 2017, Soldanski said, citing a staff briefing by company managers earlier on Monday.
Including job cuts in related trades, layoffs in the northwestern town of 165,000 may exceed 900, Soldanski said.
Valmet acquired the roof-making unit from German contract carmaker and cabrio specialist Karmann in 2010 after the company had filed for insolvency.
Europe's largest automotive group Volkswagen currently builds the drop-top version of its best-selling Golf hatchback at a separate plant in Osnabrueck employing 1,900 people which also assemble Porsche sports cars.
Valmet in Finland declined to comment.
Reporting by Andreas Cremer, additional reporting by Jussi Rosendahl in Helsinki