TOKYO (Kyodo) -- Japan expressed concerns Tuesday over China's recent decision to expand export controls on rare earths that led U.S. President Donald Trump to threaten an additional 100 percent tariff on Chinese imports beginning next month.

Japanese Foreign Minister Takeshi Iwaya told a press conference that Japan is deeply concerned about the impacts of Beijing's move, announced Thursday, on global supply chains.

China dominates the global supply of rare earths and other minerals vital for various modern technologies, from electric vehicles to weapons systems.

"We have been making requests to China at various levels, including through Foreign Minister Wang Yi, to ensure that global supply chains will not be affected further by its export controls," Iwaya said.

According to Japan's top diplomat, Beijing has told Tokyo that it will handle the issue properly, but concerns persist.

"We'll continue to cooperate with related countries and respond with necessary steps," Iwaya said.

On Sunday, Trump said he thinks U.S.-China relations will be "fine" despite renewed trade tensions following his most recent tariff threat.