Despite Glencore cutting its Australian thermal coal output by 15 per cent in February, prices for the bulk commodity have continued to slide amid a dramatic slump in demand from China.

Thermal coal prices are now below $US60 per tonne, and Mr Freyberg told an audience in Newcastle on Wednesday that the company's remaining mines were being reviewed.

"We continue to review our operations in the current market environment," he said.

"We won't and can't run mines that don't make a financial contribution."

Mr Freyberg said his mine managers had been told to "challenge every input cost into the business", which he said would likely affect suppliers and mining services companies, which have already suffered as mining companies cut spending.

Wild gyrations 

The comments come after wild gyrations in Glencore's share price in recent weeks, typified by a single-day fall of almost 30 per cent last week and a temporary spike of more than 70 per cent in its Hong Kong shares on Monday.

Some of that volatility has stemmed from concerns about the transparency and debt obligations attached to Glencore's trading business, which Mr Freyberg sought to explain to the audience.

The Queensland government has in recent years toyed with the prospect of reducing royalties or helping to fund rail infrastructure in a bid to help coal miners such as Adani push ahead with development of their projects in Queensland's Galilee Basin.

Mr Freyberg said the miner was opposed to governments funding new entrants.

"Bringing on additional tonnes with the aid of taxpayers' money would materially increase the risk to existing coal operations," he said

He also took a swipe at the privatisation of former government rail and port operators if it meant "unreasonable" tariff increases every year.

Glencore is one of several coal miners involved in the Wiggins Island Coal Export Terminal in dispute with former government rail company Aurizon over fees.