BHP Billiton has played down suggestions that it could delay its $20 billion Port Hedland harbor expansion as softening demand and stubbornly high costs force miners to review spending plans.

Chairman Jacques Nasser said in May that BHP was rethinking its plans "every day" as the economy deteriorated and put the brakes on an $80 billion plan, outlined in 2011, to grow the company's iron ore, copper and energy operations.

Building an outer harbor at Port Hedland, one of Australia's biggest ports, is one of the top three projects BHP outlined in its $80 billion plan. The port development has long been seen as the project most likely to go ahead, even as the company pares spending in response to global uncertainty and shareholder jitters.

The investment is crucial if BHP is to double iron ore production to 440 million tons a year as planned. But analysts have begun to question all projects after China's growth rate slowed to its slackest pace in more than three years in the second quarter.

The miner confirmed on Thursday that Jimmy Wilson, who took the helm of the iron ore division last month, had sent a note to employees about the challenges facing the market, but also on long-term prospects and the company's "commitment to our projects currently in execution".

"He reiterated what we've been saying for some time; that we are reviewing the sequence and pace of our future growth projects in the current environment," a BHP spokesman said.

"However, he did not say anything about Outer Harbor approvals and the fact remains that no decision has been made on the project."

The outer harbor will take about eight years to complete, at a cost analysts estimate at more than $20 billion. Once finished, it would be able to handle 240 million tons of iron ore a year, adding to the 220 million tons the company is targeting in an inner-harbor expansion already under way.

The development would include a 4km jetty, a four-berth wharf and a 32km shipping channel.

The Australian newspaper reported at the weekend that BHP could delay a decision on the $30 billion proposed expansion of the Olympic Dam mine in South Australia.

BHP declined to comment directly on the report but said there was no change in the status quo. (Reuters)