General Motors has stepped up negotiations with rival suitors to offload a stake in Opel, its European carmaking business, and could sign at least one memorandum of understanding this week as talks with Magna International, the preferred bidder, have hit obstacles.

RHJ International, the Belgium-based industrial holding company interested in Opel, had improved its earlier bid and GM was “taking it very seriously”, said a person close to the sale process on Monday, who added that a memorandum could be signed within days.