Rio Tinto bumps up iron ore guidance after strong Q1

But it also reported a sharper-than-expected 16 percent fall in copper production at a time when the metal's price is forecast to show strong gains, raising some concerns among analysts and possibly leading to downgrades to full-year forecasts.

Judging by the market's modest sell-off following the release, the report does seem to be slightly on the low side, said Ben Potter, market strategist with brokerage IG Markets.

Rio Tinto edged 0.06 percent down in a firmer overall market.

Peter O'Connor, global head of mining research for Bank of America Merrill Lynch, believes the Anglo-Australian miner can meet its iron ore target, but is concerned about the copper shortfall.

Copper was disappointing in the first quarter and importantly won't be made up during the year, O'Connor said.

Rio Tinto said it expected to produce about 234 million metric tons of iron ore this year from mines in Australia and Canada, including mining partners' interests, a slight upgrade from previous guidance of 230 million metric tons.

In the first quarter, most of our operations continued to run at capacity, Rio Tinto Chief Executive Tom Albanese said in the company's production report.

Chinese demand grew strongly and we saw some recovery in OECD markets, but we are still cautious about short-term volatility, Albanese said.

His comments suggested fears of a double-dip global recession were unfounded. They were strongest yet by a major miner along these lines. So far, Rio Tinto and its major rivals have been more cautious in calling an end to the global downturn.

Close peer BHP Billiton is expected to give a similar assessment when it reports production data on April 21.

Rio Tinto also said capital expenditure would be at least $5 billion this year, with potential for a further $1 billion, as it looks to develop more iron ore and copper mines.

Rio Tinto's aluminum production fell 1 percent in the quarter from a year earlier.

Spot iron ore prices <.I062-CNI=SI> rose 9 percent in the quarter, aluminum 4 percent and copper 6 percent, with forecasters seeing more price rises in the second quarter.

Rio Tinto is the world's largest aluminum producer and the second biggest iron ore miner after Brail's Vale .

The drop in mined copper output was primarily due to lower grades at its Kennecott Utah Copper unit and its part-owned Grasberg mine in Indonesia operated by Freeport McMoran .

Kennecott's contribution in the current quarter will also be lower, owing to a 19-day smelter maintenance shutdown.

Rio Tinto also holds a 30 percent stake in Chile's Escondida copper mine. Its share of Escondida's mined copper output fell 7 percent in the first quarter, while refined copper production dropped 20 percent, owing to some safety-related downtime.

(Editing by Mark Bendeich)