Washington, July 8 (RHC)-- U.S. President Donald Trump on Tuesday formally started the withdrawal of the United States from the World Health Organization, making good on threats to deprive the UN body of its top funding source over its response to the coronavirus.

Public health advocates and Trump's political opponents voiced outrage at the departure from the Geneva-based body, which leads the global fight on maladies from polio to measles to mental health -- as well as COVID-19, at a time when cases have again been rising around the world.

After threatening to suspend the $400 million in annual US contributions and then announcing a withdrawal, the Trump administration has formally sent a notice to UN Secretary-General Antonio Guterres, a State Department spokesperson said.

The withdrawal is effective in one year -- July 6, 2021 -- and Joe Biden, Trump's presumptive Democratic opponent, is virtually certain to stop it and stay in the WHO if he wins the November election.

A spokesman for Guterres and the global health body itself confirmed that the United States, a key founding WHO member, gave its notice.  In a speech earlier in the day, WHO chief Tedros Adhanom Ghebreyesus said of COVID-19: "National unity and global solidarity are more important than ever to defeat a common enemy."

In line with conditions set when the WHO was set up in 1948, the United States can leave within one year but must meet its remaining assessed financial obligations, the UN spokesman said.