PM warning over China coal ban assumptions

The prime minister insists a reported ban on Australian coal exports entering China is just an issue of local rules and not a wider problem between the two countries.

There are fears the reported action by Chinese customs officials at the northern port of Dalian could be part of retaliation by the Asian giant over the coalition's stance on telecoms group Huawei.

But Scott Morrison says he has not seen any evidence to suggest it relates to that or other tensions between the countries.

"I think people should be careful about leaping to conclusions about this," he told reporters in Auckland, where he met the New Zealand prime minister on Friday.

"This is not the first time that on occasion, local ports make decisions about these matters.

"We will, of course, continue to engage with those local ports and those authorities and work through the same regulatory issues that we have worked through in the past."

The northern port of Dalian has enacted the ban and will also cap overall coal imports from all sources for 2019 at 12 million tonnes, Reuters reported, citing an unnamed official at Dalian Port Group.

BHP said earlier in the week delays for coal importers unloading across China had more than doubled to about 40 days, but that all suppliers were facing the same issue.

Trade Minister Simon Birmingham on Thursday night asked Australia's ambassador in Beijing, Jan Adams, to seek clarification from the Chinese government.

"I'm aware of unconfirmed and unsourced media reports and have asked our ambassador in Beijing to urgently clarify their veracity," he told AAP in a statement.

"We continue to engage closely with industry on matters of market access ... China is a valued partner of Australia and we trust that our free trade agreement commitments to each other will continue to be honoured."

He warned against rushing to blame the apparent impasse on diplomatic tensions with China.

Treasurer Josh Frydenberg also warned against jumping to conclusions, insisting the Australia-China relationship remains strong.

He noted both the value and volume of Australia's coal exports to China were larger in the final quarter of 2018 compared with the previous year.

In 2018, Australia exported 89 million tonnes of coal to China, worth $15 billion, just shy of a quarter of our total coal exports.

The Dalian port received seven million tonnes of that.

Mr Morrison said he "certainly wouldn't think it was wonderful" if there was any weakening in that market.

"It would have a very serious impact on the Australian economy, and I would be concerned about it, and I would act upon it," he said.

The Australian dollar fell overnight after reports of a ban broke, but rallied on Friday morning in the face of reassuring comments from ministers.

Opposition Leader Bill Shorten says the coalition government needs to get to the bottom of what's going on.

A Department of Foreign Affairs and Trade official told senators on Thursday night it could be that China was managing domestic supply issues, but noted the uncertainty around "unsourced, unconfirmed reports" was having a real impact.

Asked about the purported ban, China foreign ministry spokesman Geng Shuang said customs officers were continually inspecting and testing imports for safety and quality "to safeguard importer rights and interests and protect the environment".

Beijing has been trying to restrict imports of coal more generally to support domestic prices.