The U.S. is asking American companies to stop shipping goods to more than 600 foreign parties over fears the items could be diverted to Russia for use in its invasion of Ukraine, a U.S. official said on Thursday. The Commerce Department sent letters in recent weeks to at least 20 companies with the warning, the latest effort to stymie the Russia war effort in Ukraine, a U.S. Commerce Department official said. The companies make and sell products found in missiles and drones recovered inside Ukraine.