Tempers flared in the U.S. Congress on Wednesday after its chief physician urged lawmakers to resume wearing masks to slow the spread of the highly contagious Delta variant of COVID-19, with the top Democrat labeling Republican opposition as "moronic."

A high-ranking aide to House of Representatives Speaker Nancy Pelosi stopped short of confirming a report based on garbled audio that Pelosi called her Republican counterpart "such a moron" because of his opposition to the new directive.

The high-level spat came as Covid-19 cases in recent days have been rising, along with deaths, across the United States.

-Reuters -