MELBOURNE - Major miners and their lobbyists have asked Canberra for help in pushing back against China's efforts to extract better terms for their iron-ore, including raising the prospect of a single selling desk for Australia's most valuable commodity export, senior government officials said on Friday.

China's State iron ore buyer, China Mineral Resources Group (CMRG), has been using increasingly hardball  tactics against mining giants to win better deals for the country's steel mills, to tighten its grip on the $132-billion seaborne market.

The push by miners comes after CMRG blacklisted some of BHP's iron-ore for seven months, during protracted contract talks. CMRG has also told some steelmakers not to engage in discussions with Fortescue about a new iron ore product.

Australia is the biggest supplier of iron-ore to China, accounting for more than 50% of its imports.

Canberra watches that market closely as China is the country's biggest trading partner and iron ore the most
lucrative commodity export, expected to reap A$114-billion ($81-billion) in the current financial year, according to government estimates.

A Senate panel on Friday asked Department of Foreign Affairs and Trade officials whether they had received a request from BHP, Fortescue, Rio Tinto, Hancock, or the Minerals Council for government intervention or support in relation to CMRG and iron-ore pricing.

Steven Yates, an assistant secretary in the department,
confirmed they had.

"Yes, I can say that we have engaged with those miners, and during the course of those discussions there have been suggestions on ways that we might be able to carry this issue forward," Yates said, declining to offer more detail for reasons of commercial confidence.

"We engage very regularly with Australian miners, and I try to support them as best as possible to ensure that they can continue to export their iron ore and receive the best price as possible," he said.

The Senate panel also asked for a response "to the proposition raised in industry circles that Australia needs some sort of export-side coordination to cover a single state buyer."

Deputy Secretary George Mina replied that previous plans in the agriculture sector to coordinate on supply had not been well-received by trading partners, but this instance is different as "there is already an established single buyer".

"So there's clearly these questions for long-term strategy," Mina said.

BHP, Rio Tinto, Fortescue and Hancock declined to comment.

One investor told Reuters an executive at a top iron-ore miner had mentioned they had flagged the issue to the government but said Canberra has been trying to repair its relationship with China so might not want to take up this fight right now.

BHP reached a deal with CMRG in April, which included agreeing to some yuan-denominated sales.

China is currently in negotiations with Fortescue and will enter annual contract talks with Rio Tinto later this year.