Opel, the German subsidiary of General Motors, is to spin off its car parts business into a joint venture with US firm Caterpillar, the business daily Handelsblatt reported on Wednesday. Opel chief Hans Demant has agreed with the US group to transfer up to 1,200 employees from Opel's factories in Bochum, Rüsselsheim and Rome to the combined entity, the newspaper said, quoting company sources. The German cartel authorities had already approved the venture, it added. Handelsblatt said that GM had declined to comment on the information. Opel's works council had agreed to the deal on condition there were job guarantees for at least 10 years, it said.