Increased tensions ahead of trade negotiations between the United States and China knocked down stocks on Wall Street on Tuesday and stretched the market’s losses deeper into a fourth week.

Washington blacklisted a group of Chinese companies after claiming that their technology plays a role in the repression of China’s Muslim minority groups. The latest move casts more doubt on whether the world’s two largest economies will find a resolution to their long-running and economically damaging trade war. Envoys from the U.S. and China are preparing for another round of negotiations this week.

“The jockeying for position in front of the Thursday and Friday meetings in Washington has intensified perhaps more than the market could have imagined,” said Julian Emanuel, chief equity and derivatives strategist at BTIG.