WASHINGTON (AP) — The Senate's top Democrat said Friday that he'll block two of President Donald Trump's key nominees unless the Commerce Department picks up the pace on its investigation of China's trade practices involving the aluminum and steel industries.

Minority Leader Chuck Schumer of New York said he'll hold up two Commerce Department undersecretaries until Commerce Secretary Wilbur Ross stops "foot dragging on this critical investigation" of China's subsidies of the two industries.

The administration in August announced that it would investigate whether China's aluminum and steel industry trade practices are a national security threat to the U.S. That could lead to a crackdown on imports.

Schumer says the probe isn't going anywhere and that for all his tough talk President Trump hasn't cracked down on China's trade practices.

"President Trump repeatedly promised to champion fair trade policies and crack down on predatory trade practices from countries like China that massively subsidize their steel and aluminum products and hurt American workers," Schumer said. "Unfortunately, when it comes to being tough on China to level the playing field for American steel and aluminum workers, it's clear President Trump has been nothing more than a paper tiger."

Schumer has placed a "hold" on the nominations of Gil Kaplan to be under secretary of commerce for international trade and Nazakhtar Nikakhtar to serve as assistant secretary of commerce, industry and analysis. That means he would force majority Republicans to spend precious Senate floor time debating the nominations.