Updated from 1:17 a.m. EDT

RHJ International confirmed Monday it is negotiations with General Motors ( symbol) about an acquisition of a majority stake in GM's European unit Opel.

"These discussions have been taking place over a number of weeks and are at an advanced stage," RHJ said in a brief statement.

It was reported by the Financial Times that RHJ was putting together an improved offer for Opel with plans to present the offer to GM either Monday or Tuesday, a report says.

RHJ thinks it has improved chances of winning the deal as negotiations between GM and Canadian auto-parts maker Magna Internationall ( MGA), which is seen as the leading bidder, have run into obstacles such as disagreements over intellectual property, the Financial Times reports, citing people familiar with RHJ's plans. Magna, together with Russia's Sberbank, signed a memorandum of understanding for a stake in Opel in May.

Talks between the U.S. automaker, which emerged from bankruptcy on Friday, and RHJ, a Belgium-based holding company that is linked to buyout firm Ripplewood, continued through the weekend at GM's European headquarters in Zurich, the newspaper reports.

RHJ will say it needs a smaller amount of German government guarantees to finance the deal than Magna -- 3.8 billion euros, compared with the 4.5 billion euros Magna is seeking. RHJ is targeting a stake of about 51% to 55% in Opel, the Financial Times reports.

GM was unavailable for comment on Sunday. Ray Young, its chief financial officer, told the Financial Times on Friday that while Magna had "a head start" in the bidding for Opel, RJH "have moved up very quickly."