New Chinese export restrictions have left American companies’ U.S.-bound face masks, test kits and other medical equipment urgently needed to fight the coronavirus stranded, according to businesses and U.S. diplomatic memos.

Large quantities of critical protective gear and other medical goods are sitting in warehouses across China unable to receive necessary official clearances, said some suppliers and brokers.

Health-care equipment maker PerkinElmer Inc., based in Massachusetts, is unable to ship 1.4 million test kits for Covid-19, the disease caused by the new coronavirus, from its Suzhou factory because it lacks a certification required by the new rules, according to a State Department memo reviewed by The Wall Street Journal.

A Shanghai vice mayor told Minnesota-based conglomerate 3M Co. that the city “relies on 3M’s locally produced N-95 respirators for its Covid-19 prevention efforts and lacks viable alternatives,” a second memo said. The official “signaled that lifting restrictions on distribution of the company’s masks would require instructions from Beijing,” the memo said.

PerkinElmer said it is working with the Chinese government to clear the test kits. 3M said it has received shipments from China and is working to coordinate more, though fewer planes are available than usual.