Rio Tinto Group (ASX:RIO) and Japan's Sumitomo Metal Mining signed final joint venture agreements to develop the Winu copper-gold project in Western Australia, according to a Monday statement by the company.

Under the terms, Sumitomo will acquire a 30% stake for up to AU$430.4 million, per the statement. Rio Tinto will continue to develop and operate the project.

The transaction, subject to regulatory approvals, is expected to close later this year, along with a pre-feasibility study and environmental review document for the project, Rio Tinto said.