China has reportedly ordered its airlines to halt all incoming deliveries of US-made Boeing aircraft in response to Donald Trump’s 145 per cent tariffs on Chinese goods.

In deals worth billions of dollars, China’s three main airlines were expected to take delivery of 179 Boeing planes by 2027. The orders are larger than the entire Qantas main fleet.

Those deliveries have been put on hold, according to reports from Bloomberg News.

Boeing CEO Kelly Ortberg previously said that the company supported 1.8 million jobs in the United States.

A delivery freeze would have direct consequences for the group, which traditionally receives 60 per cent of the sale price upon delivery.

Postal ban

In Hong Kong, meanwhile, the Chinese special administrative region’s postal service has said it will stop shipping goods to the US in response to impending higher tariffs on items from the territory.

A “de minimis” exemption that allows postal items from China valued at US$800 ($A1259) or less to enter the US duty-free, ends on May 2.

Hongkong Post in a statement said, it “will definitely not collect any so-called tariffs on behalf of the US”, referring to the levies as “unreasonable and bullying acts”.

Hongkong Post will also stop accepting items sent by sea with immediate effect, air mail will be suspended from April 27.

Mineral probe

The moves against the US come as Trump has ordered a probe into potential new tariffs on all US critical minerals imports, in an attempt to push back on industry leader China.

The order lays bare what manufacturers, industry consultants, academics and others have long warned Washington about: That the US is overly reliant on Beijing and others for processed versions of the minerals that power its entire economy.

China is a top global producer of 30 of the 50 minerals considered critical by the US Geological Survey, for example, and has been curtailing exports in recent months.

Trump signed an order on Tuesday local time directing US Commerce Secretary Howard Lutnick to begin a national security review under Section 232 of the Trade Expansion Act of 1962.

That is the same law Trump used in his first term to impose 25 per cent global tariffs on steel and aluminium and one he used in February to launch a probe into potential copper tariffs.

US dependency on minerals imports “raises the potential for risks to national security, defence readiness, price stability, and economic prosperity and resilience”, Trump said in the order.

Within 180 days, Lutnick is required to report his findings to Trump, including whether to impose tariffs. Were Trump to then impose a tariff on a nation’s critical minerals, the rate would supersede the reciprocal tariffs he imposed earlier this month, according to the White House.

The US currently extracts and processes scant amounts of lithium, has only one nickel mine but no nickel smelter, and has no cobalt mine or refinery. While it has several copper mines, the US has only two copper smelters and is reliant on other nations to process that key red metal.

Earlier in April, Beijing restricted exports of rare earths in response to Trump’s tariffs, a move that further exacerbated supply concerns among US officials.

Rare earths are a group of 17 elements used across the defence, electric vehicle, energy and electronics industries. The United States has only one rare earths mine and most of its processed supply comes from China.

-with AAP