Afghanistan, Jan. 25 -- The World Health Organization expressed regret over the United States' withdrawal, warning the decision could weaken cooperation and increase global health insecurity.

The World Health Organization said it deeply regrets the United States' decision to withdraw, warning that the move risks making both the country and the wider world less secure.

The United States formally exited the World Health Organization on Thursday, saying it intends to pursue bilateral cooperation with countries on disease surveillance and public health issues.

WHO said the United States, as a founding member, played a critical role in historic achievements, including smallpox eradication and progress against polio, HIV/AIDS and Ebola.

The W...