Belgian investment company RHJ International SA (RHJI.BT) is interested in buying between 50% and 55% of General Motors Corp.'s (GM) Adam Opel GmbH European unit, a person close to the matter told Dow Jones Newswires Monday.

The Brussels-based company might also have a contract ready for signature with GM as early as Wednesday, as "things are moving very quickly," the person also said.

RHJ International said earlier Monday it is in advanced talks with GM to acquire a stake in Opel.

-By Alessandro Torello, Dow Jones Newswires; +32 2 741 14 88; alessandro.torello@dowjones.com