BEIJING (AP) — China has ordered importers of U.S. sorghum to pay deposits for possible higher tariffs in an anti-dumping investigation, adding to mounting trade conflicts with Washington.

The Commerce Ministry said Tuesday in a preliminary ruling that U.S. sorghum was being sold at improperly low prices. It said importers must post bonds of 178.6 percent of their goods to cover possible anti-dumping duties while the probe is completed.

Tensions with Washington have worsened after President Donald Trump threatened to hike tariffs on Chinese goods in a dispute over technology policy. Beijing has released its own list of U.S. goods for possible retaliation.