Chinese exports of rare-earth minerals are all but on hold as producers grapple with tighter permit requirements following last week’s new restrictions on the critical materials in an escalating trade war with the US.

The delays could take weeks to clear as questions including code classifications are clarified, according to people with knowledge of the issue. Companies are rushing to submit documents to apply for export permits but those can take about 45 working days, the people said, asking not to be named as they are not authorized to speak to the media.

The latest list of restricted rare earths includes samarium, gadolinium, terbium, dysprosium, lutetium, scandium and yttrium, used in displays and powerful magnets, plus crucial medical and even defense technology. Two of the most common rare earths — neodymium and praseodymium — weren’t included. Analysts said China may have targeted elements that are more scarce overseas.

The delays will mean some buyers outside of China could be left short of supply and face production cuts, the people said.

The latest controls are expected to have broad impacts in the US, Europe and Japan due to the wide usage of the minerals, which also includes optical lasers, radar devices, magnets for wind turbines, jet engine coatings and other advanced technologies.

Other critical minerals placed under similar export controls in the last two years, such as gallium, germanium, antimony, saw export volumes crash to zero for months after controls were rolled out, as exporters need time to get certified.