President Donald Trump’s decision to exit the World Health Organization means the U.N. agency is losing its biggest funder.

World Health Organization chief says agency already cutting back on hiring and travel with Trump withdrawal set to hit funding.

Tania Cernuschi, a WHO staff member of 10 years who has worked on improving vaccine access, said she thought of the campaign when she could not sleep after Trump's announcement.

The United States will leave the World Health Organization, President Donald Trump said on Monday, saying the global health agency had mishandled the COVID-19 pandemic and other international health crises.

In this April 15, 2020 file photo, the logo and building of the World Health Organization (WHO) headquarters in Geneva, Switzerland.

The U.S. has traditionally been the most generous benefactor of the WHO. A Trump executive order to cut ties with the WHO could pose a threat to global public health.

The World Health Organization is drawing up a list of reasons why the U.S. should remain in the WHO for its own good, two sources familiar with the process told Reuters, as part of an attempt by its supporters to lobby incoming President Donald Trump.

By withdrawing from the World Health Organization and overhauling aid, Trump's new executive orders endanger Americans and the globe, researchers warn. The move also cedes U.S. power to other nations.

WHO’s constitution, drafted in New York, doesn’t have a clear exit method for member states. A joint resolution by Congress in 1948 outlined that the U.S. can withdraw with one year's notice. This is contingent, however, on ensuring that its financial obligations to WHO “shall be met in full for the organization’s current fiscal year.”

The World Health Organization said Friday it was reviewing its priorities ahead of the withdrawal of its largest donor the United States, noting the agency provides vital services to protect against health threats.

Public health experts say the United States’ departure could cripple the WHO’s operations or leave an opening for China to assume greater control over the agency.

By Patrick Wingrove, Jennifer Rigby and Emma Farge NEW YORK/GENEVA (Reuters) - The United States will leave the World Health Organization, President Donald Trump said on Monday, saying the global health agency had mishandled the COVID-19 pandemic and other international health crises.