President Donald Trump said on Saturday he may consider rejoining the World Health Organization, days after ordering a U.S. exit from the global health agency over what he described as a mishandling of the COVID-19 pandemic and other international health crises.

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.

Ooh, that’s a big one,” Donald Trump said Monday as he signed an executive order – one of dozens during his first hours as president – to withdraw the United States from the World Health Organization.