Canadian uranium miner Cameco Corporation is set to bag a 70% stake in the East Pilbara yellowcake project, which it plans to operate in a JV with Japan's Mitsubishi Corp. The Japanese company will hold the remaining 30% interest.

The deal, expected to be wrapped up in August following approvals from the area's traditional landowners, is part of Rio's planned $US15 billion ($A15.7 billion) asset sell-off aimed at repaying the significant debt racked up last year through its acquisition of Canadian aluminium group Alcan.

The Kintyre sale has added further fuel to talk that Rio is set to sell off some of its American coal assets, edging the miner closer to its $US10 billion asset divestment target for 2008.

Earlier this year Rio sold off its Green Creek mine in Alaska for $US750 million and its interest in the Nevada Cortez operation for $US1.695 million.

Rio Tinto chief financial officer Guy Elliot said the Kintyre transaction, along with other recent sales, demonstrated the miner's ability to harness "real value" for its assets.

"These transactions bring transparency to the value inherent in Rio Tinto's portfolio of high quality assets," Elliot said in a statement.

According to Cameco, the Kintyre project, some 270km northeast of Newman, is estimated to contain up to 80 million pounds of uranium, averaging grades of 0.3-0.4%.

The tenements comprise a string of granted mining leases, lease applications and prospecting licences across 52 square kilometres.

Rio's shares shed $1.25 to $121.90 in morning trading.