By Hyunjoo Jin

April 23 (Reuters) - Tesla TSLA.O CEO Elon Musk said on Tuesday that the production of its Optimus humanoid robots had been affected by China's export restrictions of rare earth magnets.

He said China wants assurances that its rare earth magnets are not used for military purposes, adding that the automaker is working with Beijing to get an export license to use rare earth magnets.

"China wants some assurances that these are not used for military purposes, which obviously they're not. They're just going into a humanoid robot," he said during an earnings conference call, adding that it's not a weapon.

This month, China placed export restrictions on rare earths as part of its sweeping response to U.S. tariffs, restricting the supply of minerals used to make weapons, electronics and a range of consumer goods.

The export curbs include not only mined minerals but magnets and other finished products that will be difficult to replace, analysts said.

Exporters must now apply to the Ministry of Commerce for licenses, a relatively opaque process that can range from six or seven weeks to several months.

Musk has said he expected Tesla to make thousands of Optimus robots this year.

(Reporting by Hyunjoo Jin. Editing by Gerry Doyle)

((hyunjoo.jin@thomsonreuters.com; 82-2-3704-5685; Reuters Messaging: hyunjoo.jin.thomsonreuters.com@reuters.net))