China said it started a one-year anti-subsidy investigation into grain sorghum imported from the U.S., further fueling trade tensions between the world’s two biggest economies.

The Commerce Ministry said it has initial evidence that the U.S. government subsidizes grain sorghum, according to a statement released Sunday. The ministry said it will probe imports from January 2013 to October 2017 and while it aims to complete the inquiry by next February, it could potentially extend until August 2019.

“The surging amount of imports from the U.S. since 2013 has dragged down market prices, damaging China’s grain sorghum sector,” Wang Hejun, chief of the ministry’s trade remedy and investigation bureau, said in a separate statement Sunday on the agency’s website.

The latest spat comes days after U.S. President Donald Trump slapped tariffs on imported solar panels and washing machines, which Beijing called a “misuse” of trade measures. Trump also is considering whether to impose tariffs on imported steel and aluminum, while the U.S. Trade Representative’s office is probing China’s intellectual-property practices.

If China wanted to hit back on trade, agricultural products such as soybeans could be a weapon as U.S. grain and beef feed the increasing demands of Chinese customers.