The heads of four major labor unions on Wednesday called on President Donald Trump to boost American shipbuilding and enforce tariffs and other “strong penalties” against China for its increasing dominance in that sphere.

The presidents of the United Steelworkers, International Brotherhood of Electrical Workers, International Brotherhood of Boilermakers and International Association of Machinists and Aerospace Workers argue that China’s efforts have hurt American workers and national security.

In the letter obtained by The Associated Press, they urged Trump to “impose tough penalties against vessels built according to the plans, policies, and actions of the Chinese Communist Party and to adopt complementary policies that rebuild America’s shipbuilding capacity and workforce.”

Last year under President Joe Biden, the unions filed a petition seeking to address China’s shipbuilding under Section 301 of the 1974 U.S. Trade Act, hoping to start a process by which tariffs and other measures could be enacted.