The world's third-largest iron ore miner said it was deferring a project to boost the handling capacity at its Port Hedland iron ore port, delaying a planned ramp up in production and cutting costs.

While the delay would affect only around 20 million tonnes of iron ore, a tiny amount compared with seaborne trade of around 1.3 billion tonnes, analysts said it was significant given BHP's position as a leading producer.

"It is probably more a symbolic posturing position by BHP, but it also likely signals the bottom of the iron ore market, given this action is being taken by one of the lowest cost producers," said Mark Pervan, head of commodities for ANZ Bank.

Spot iron ore prices have fallen 60 percent over the past year following a massive rise in production, which analysts and some mining executives blame on overestimates of China's appetite for imported ore by mega miners BHP, Vale and Rio Tinto .

However, analysts said small adjustments in supply were unlikely to have much impact on prices that have tumbled to around $50 a tonne from almost $200 four years ago.

"Demand is the saviour," said Joel Crane, a commodities analyst at Morgan Stanley.

"The sort of tonnes we're talking about are drops in the ocean. If you're going to see a sustained stabilisation in the iron ore price, you're going to need a demand pick-up."

COST SAVINGS

BHP, which said its iron ore output climbed 20 percent to58.9 million tonnes in the March quarter versus a year ago, had expected to reach annual output of 290 million tonnes by June2017. It did not set a new date.

The company revised up its 2015 full-year production guidance on a 100 percent basis by 2 percent to 250 milliontonnes, and said it was on track for 270 million tonnes without further investment.

"While (the deferral) will lead to a slower path to system capacity of 290 million tonnes per annum (Mtpa), it will come at a lower capital cost," BHP said in its March quarter report.

Work to reduce congestion at the export terminal at PortHedland had been expected to cost about $600 million, RBC Capital said.

"In iron ore, our focus remains on producing at the lowest possible cost with Western Australia iron ore unit costs now below $20 per tonne as we continue to improve productivity, “Chief Executive Andrew Mackenzie said in a statement.

Big miners such as BHP and Rio have been able to cut costs more than smaller rivals, leaving them better able to weather the downturn in prices.

Prices of the steel-making material stood at $50.80 a tonne on Wednesday .

Rio Tinto on Tuesday reported a 12 percent rise quarterly output to 74.7 million tonnes, signalling it was on track to yield 350 million tonnes in calendar 2015.

"I don't believe Rio will go down the same path, given they are much more reliant on iron ore for revenue than BHP. Rio has made it clear it is committed to its next expansion to 350million tonnes," said David Lennox, mining analyst with Fat Prophets.

Analysts differ on the direction of iron ore prices.

Barclays is forecasting an average 2015 price of $56 atonne, while Citi expects iron ore to average just $37 a tonne over the second half and only rise to about $40 by 2019.