GENEVA, May 15 (Xinhua) -- The UN Refugee Agency UNHCR and the World Food Program (WFP) on Monday vowed to jointly step up support for desperate refugees fleeing South Sudan.

In an updated response plan presented here in Geneva on Monday, the two agencies said that they are seeking 1.4 billion U.S. dollars to provide life-saving aid to South Sudanese refugees in the six neighboring countries until the end of 2017.

The South Sudanese refugee response plan so far remains only 14 percent funded, they said.

"Bitter conflict and deteriorating humanitarian conditions in South Sudan are driving people from their homes in record numbers," said UN High Commissioner for Refugees, Filippo Grandi.

According to the UN information, the situation in South Sudan continues to worsen, with a combination of conflict, drought and famine leading to further displacement and a rapid exodus of people fleeing one of the world's most severe crises.

A UN source said that with more than 1.8 million refugees, one million of them are children, having sought safety in the neighboring countries, South Sudan has now become the world's fastest growing refugee crisis.

UNHCR said that the current rate of people fleeing South Sudan exceeds the humanitarian community's already pessimistic estimates, and the number of people fleeing to Sudan in March surpassed the expected figure for the entire year.