China has a virtual monopoly on those 17 metallic elements, which are critical components to everyday products from cars to jet engines to electronics like smartphones and flat-screen TVs. They’re even crucial for the contrast dye used in MRI machines and some cancer drugs.

China returns to trade talks with the U.S. holding, from its view, a strong hand: Its economy is bearing up better than expected. And it has an ace card: rare earths.

Wall Street's main indexes opened subdued on Tuesday as investors awaited the outcome of ongoing trade talks between the United States and China aimed at cooling a tariff dispute that has bruised global markets this year.