The United States will pay more than $200 million to the World Health Organization by the end of the month after reversing Donald Trump's plan to withdraw, Secretary of State Antony Blinken has said. 

The sum amounts to the commitments the United States had made to the global health body, to which it has been the largest donor. 

"This is a key step forward in fulfilling our financial obligations as a WHO member and it reflects our renewed commitment to ensuring the WHO has the support it needs to lead the global response to the pandemic," Mr Blinken told a virtual UN Security Council session on Covid-19. 

"The United States will work as a partner to address global challenges. This pandemic is one of those challenges and gives us an opportunity not only to get through the current crisis, but also to become more prepared and more resilient for the future." 

Secretary of State Blinken said the United States would also "provide significant financial support" to Covax, a global plan to distribute vaccines to the poorest nations. 

President Trump - who faced criticism for his handling of Covid in the United States, which has suffered the highest death toll of any nation - announced a withdrawal from the World Health Organization, saying it was beholden to China and did not do enough to stop the pandemic. 

President Joe Biden immediately reversed the decision although his administration has also pressed China to be more forthcoming to a WHO team investigating the origins of the devastating virus. 

"All countries must make available all data from the earliest days of any outbreak," Mr Blinken said. 

"And going forward, all countries should participate in a transparent and robust process for preventing and responding to health emergencies so the world learns as much as possible, as soon as possible."