RIO Tinto's uranium subsidiary Energy Resources of Australia has reaffirmed its forecast for normal full-year production -- despite warning that output is set to dip in the second quarter as water in the pit blocks access to high grade ore.

Analysts moved yesterday to trim their production forecasts but ERA said it was still expecting "normal" uranium oxide production of somewhere between last year's 5400 tonnes and the record production of 5900 tonnes in 2005.

ERA operates the Ranger uranium mine in the Northern Territory.

"We expect production to return to normal levels," ERA spokeswoman Libby Beath told The Australian.

ERA earlier reported disappointing first-quarter production of 1327 tonnes at Ranger, down 15 per cent from the fourth quarter of 2007. But production was up 32 per cent from a year ago, when the mine was flooded by exceptionally heavy rains.

Analysts are expecting ERA's quarterly numbers to reflect a global mining sector that is battling infrastructure bottle necks, bad weather, rising costs and labour trouble as it tries to raise production.

Tight mine supplies are a key factor sustaining metal and mineral prices at historic highs.

Rio is set to report first-quarter production today. The market wants to know its coal performance out of clogged Newcastle port, and the degree to which the wet season in northern Western Australia has hampered iron ore production.

Rio chief executive Tom Albanese is set to host a media teleconference as he seeks to use the production numbers to underline Rio's standalone value in the face of BHP's hostile $160billion bid.

BHP reports its quarterly production next week. Output is expected to be hurt by power shortages at its aluminium smelters in southern Africa, floods in its Queensland coal fields, and a strike at its Colombian nickel operation.

ERA shares initially fell as much as 2 per cent on the back of the first-quarter production numbers, but the stock recovered later in the day.

At the close, ERA shares were down 22c, or 1.1 per cent, at $20.08, valuing the miner at $3.8billion.

Rio owns 68.4 per cent of ERA.

ERA is still pumping water from the bottom of Ranger pit.

The company has almost mined down as far as it can go, and will now have to rely on processing stockpiles until the water is removed to allow access to high-grade ore.

That is expected to occur late in the second quarter.

As a result, ore grades into the mill are expected to fall to around 0.20-0.25 per cent in the second quarter compared with 0.32 per cent in the first quarter.

"The wet season is drawing to an end and water levels in the pit are substantially lower than at the same time in 2007," ERA said.

"However, currently there is restricted access to higher grade ore, which is located predominantly in the bottom of the pit."

Ore mining at Ranger was up 6 per cent from a year ago as ERA put new equipment into action to extend the open pit, and to position the company to access the higher grade ore at the bottom of the pit as soon as the water is cleared.