President Joe Biden said last month after a U.S. fighter jet shot down a suspected Chinese spy balloon that he planned to speak to Chinese President Xi Jinping about the episode and clear the air between the rival superpowers.

Five weeks later, the call still hasn’t happened.

Instead, after two months of diplomatic sniping and Xi’s trip this week to Moscow where he and Russian President Vladimir Putin jointly denounced the United States, U.S.-China relations have slid to what some say is the worst since the countries normalized ties in the 1970s.

Blinken did meet with China’s top diplomat Wang Yi at the Munich Security Conference last month after the balloon incident, but this did not soothe tensions. A source familiar with that conversation called it the most antagonistic U.S.-China engagement since contentious talks in Alaska early in the Biden administration.

The person said China had declined to coordinate the meeting, forcing the State Department’s top East Asia diplomat, Daniel Kritenbrink, to personally track down Wang Yi at the conference center to ask whether it would happen.