Energy Resources Australia (ERA) is being forced to buy uranium on the global market to meet its sales commitments as problems persist at its Ranger mine in northern Australia, the company said.

Heavy rains have flooded the mine pit and led to the suspension of processing of uranium oxide, sending output tumbling 42 per cent in the March quarter. Processing is likely to remain stalled until at least late July, the miner said.

ERA, controlled by Rio Tinto , said it would need to buy as much as 2,100 tonnes of uranium oxide from third parties to meet its sales commitments of 4,500 tonnes this year.

It also forecast a first-half loss of between $30 million and $50 million, and said it was reviewing mine operations.

"In light of this continued suspension, which has occurred immediately after a very challenging 2010, a comprehensive business review of ERA's current operations and future projects is well underway," the company said.

"The review will assess priorities, processes and future expenditure."

ERA expects to mine only around 2,400 tonnes in 2011, well below earlier guidance of near 3,800 tonnes.

Production of uranium oxide for the March quarter was 518 tonnes versus 888 tonnes in the same period last year.