The U.N.'s humanitarian aid agency says the El Nino weather phenomenon has affected 60 million people worldwide and is warning the worst impact from the droughts it causes is yet to come.

Stephen O'Brien of the Office for the Coordination of Humanitarian Affairs noted El Nino's impact and expressed concerns Tuesday about "rising acute malnutrition among children under five and the increase in water- and vector-borne diseases."

OCHA says the impact of droughts caused by El Nino is expected to peak later this year or early next year.

The agency said 13 countries are requesting $3.6 billion to help meet critical needs like food, agricultural support, water and sanitation. But OCHA said "the funding gap" for the global response to El Nino is now over $2.2 billion — and could rise.