Eight U.S. senators have asked the Obama administration to take action against China over what they say are unfair subsidies to the Chinese aluminum industry.

In an Oct. 21 letter to U.S. Trade Representative Michael Froman, reviewed by The Wall Street Journal, the senators said China’s “unfair trade practices” are “undermining the entire U.S. aluminum value chain.” The Journal has reported that federal officials recently opened investigations into aluminum imports originating in China.

The...