China has announced it is banning exports of key high-tech materials that used in military applications to the United States.

The announcement has been dubbed a “considerable escalation” in the trade war – as Donald Trump threatens sweeping tariffs on Chinese exports.

The Chinese Commerce Ministry made the announcement after Washington announced a crackdown on the Chinese computer chip-making sector. The chips are needed for advanced applications, as well as software and memory devices.

Previously Beijing had required exporters to apply for licenses to send materials such as gallium to the United States.

The commerce ministry said, “In principle, the export of gallium, germanium, antimony, and superhard materials to the United States shall not be permitted.”

This new export ban comes after previous limits on exports of the critical minerals that Beijing began rolling out last year, applying only to the U.S. market.

It is the latest escalation of trade tensions between the world’s two largest economies before Trump takes office.

There have been no shipments of wrought and unwrought germanium or gallium to the U.S. this year through October, according to Chinese customs data.

Gallium and germanium are both used in semiconductors, and germanium is also used in infrared technology, fibre optic cables and solar cells.

Nearly half (48%) of globally mined antimony came from China last year, a material which is used in ammunition, infrared missiles, nuclear weapons and night-vision goggles, as well as in batteries and photovoltaic equipment.

China has also accounted for 59.2% of refined germanium output and 98.8% of refined gallium production this year, according to consultancy Project Blue.

Project Blue co-founder Jack Bedder said, “The move is a considerable escalation of tensions in supply chains where access to raw material units is already tight in the West.”

Trump said during his presidential campaign that he would implement 10% tariffs on Chinese goods while threatening 60% tariffs on Chinese imports.