The World Health Organization (WHO) rejected Saturday a call for the Rio Olympic Games to be moved or postponed due to the threat posed by large outbreak of Zika virus in Brazil.

Responding to a call from more than 100 leading scientists, who said it would be unethical for the Games to go ahead as scheduled, the United Nations health agency said having the Games in Rio as planned would "not significantly alter" the spread of Zika, which is linked to serious birth defects.

"Based on the current assessment of Zika virus circulating in almost 60 countries globally and 39 in the Americas, there is no public health justification for postponing or cancelling the games," the WHO said in a statement.

In a public letter posted online Friday, around 150 leading public health experts, many of them bioethicists, said the risk of infection from the Zika virus is too high for the Games to go ahead safely.

"An unnecessary risk is posed when 500,000 foreign tourists from all countries attend the Games, potentially acquire that strain, and return home to places where it can become endemic," the letter said.