A deadlock on key issues including export restrictions and China’s purchases of Russian oil could reignite a tit-for-tat trade war.

The third round of negotiations between the two largest economies in less than three months wrapped up two weeks before an August 12 deadline.

U.S. and Chinese officials agreed to seek an extension of their 90-day tariff truce on Tuesday, following two days of what both sides described as constructive talks in Stockholm aimed at defusing an escalating trade war between the world's two biggest economies that threatens global growth.