Asked at a regular daily briefing whether China would step in to fill the shortfall, foreign ministry spokesman Zhao Lijian was noncommittal.

"China will look into relevant issues according to the needs of the situation," he said.

The United States is the biggest overall donor to the Geneva-based WHO, contributing more than $400 million in 2019, roughly 15% of its budget.

Zhao said the pandemic, which has infected nearly 2 million people globally, was at a critical stage and that Washington's decision would affect all countries of the world.