COVID-19 has claimed the lives of more than 177600 people and infected over 2556500 people across the world.
Speaking at a virtual press conference from Geneva, WHO Director-General Tedros Adhanom Ghebreyesus said that his organization and the U.S. Centers for Disease Control and Prevention (CDC) have a long history of cooperation and "having CDC staff means there is nothing hidden from the U.S. from day one".
"Trust us. The worst is yet ahead of us", Dr Tedros told reporters from World Health Organization headquarters in Geneva on Monday.
As of Tuesday there were more than 24,000 confirmed cases of the virus in Westchester county; 809 people had died.
He likened the coronavirus epidemic, which has globally infected almost 2.5 million people and killed more than 170,000, to the Spanish flu in 1918 that killed as many as 100 million people worldwide.
WHO's warning comes as nations like Germany and Norway have started easing restrictions put in place to fight the outbreak.
Pushing politics amid the pandemic "is like playing with fire", he added.
"It's the political problem that may fuel further this pandemic", Tedros said.
Director General Tedros Adhanom Ghebreyesus asked governments globally to unite in ending what he termed as a tragedy as he compared COVID-19 to the 1918 Spanish flu which infected at least 500 million people and killed over 50 million.
Amir Attaran, a professor at the University of Ottawa's school of epidemiology and public health and faculty of law, said more than a review was necessary, and that the WHO should lose responsibility for "anything to do with pandemic preparedness or the declaration of health emergencies".
The suit also says World Health Organization continues to defend its actions in relation to the spread of the virus, and at one time "admonished the Trump Administration that widespread travel bans and restrictions were not needed". "We don't hide anything".
He announced a decision to halt funding for the United Nations agency earlier this month; congress controls the funds.
Three New York men are suing the World Health Organization for "incalculable" damages over its response to the coronavirus pandemic.