Jordan and the UN Children's Fund issued separate appeals on Monday urging financial help for a growing number of Syrian refugees flooding the country, including children who UNICEF says are "suffering most."
Jordan said it needs $429.7 million for long-term hosting Syrian refugees while UNICEF asked for $54 million in urgent funds.
The country is hosting around 200,000 Syrian refugees -- 17,000 are sheltered at the UN-run Zaatari refugee camp in the north and half of them are children.
But record numbers have fled across the border to Jordan to flee the deadly violence at home in recent weeks and both Jordan and the UN expect their numbers to increase.
"Hosting over 150,000 Syrians is expected to cost the country about $152 million annually to cover the increasing demand on basic services and other indirect costs, in addition to $56.7 million in the form of subsidies," the Jordanian government said in a statement.
"If Syrians stay for a longer time, then there is a need for $221 million for capital expenditures," it added.
The government also expected the refugee population in the UN-run Zaatari camp to expand dramatically and reach "maybe 80,000... over the next few months of 2012."
Jordan, a desert country that faces huge water shortages and no natural resources, said these funds are needed to provide the refugees food, water, education, health care and the adequate infrastructure.
Earlier UNICEF made a similar appeal saying funds are "urgently" needed "to meet the emergency health, protection, and water and sanitation needs of the growing numbers of Syrian refugee children and their families arriving in Jordan."
"We expect to have 70,000 people at Zaatari camp by the end of this year," said the UNICEF's Jordan representative Dominique Hyde.
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UNICEF said conditions at the seven-square-kilometre (two-square-mile) Zaatari camp are "harsh, with scorching temperatures, no natural shade, and frequent sandstorms that rip through the camp."
"There was a significant increase in the number of arrivals at the camp this last weekend with more than 2,000 people crossing the border in a single night," it said.
"This number is nearly 80 percent higher than the previous largest number of Syrians crossing into Jordan within a 24-hour period."
Last week the UN High Commissioner for Refugee said that people fleeing fresh fighting in southern Syria, including in Daraa, where the uprising broke out in March last year, are pouring into Jordan in record numbers.
Last Thursday night a record 2,200 crossed the border into Jordan, the UNHCR said. Jordan's Information Minister Samih Maaytah put the number at "a record 2,324 Syrian refugees."
Maaytah said their arrivals increases pressure on Jordan and urged the international community to step up assistance to the country.
UNICEF warned, meanwhile, of the threat of disease outbreaks as the number of Syrian children refugees arriving in Jordan increases.
"This week, UNICEF is partnering with the Ministry of Health and the World Health Organisation to immunise children under five, many of whom will have missed routine vaccinations due to the violence in Syria," it said.
"UNICEF is working with partners to establish a regular vaccination programme at the camp," it said.
Hyde said children fleeing violence in Syria are at risk of suffering long-term distress without appropriate care."
"In just a few months, we expect as many as 35,000 children will be at the camp, so we urgently need to provide additional safe places and other support to protect these children who have already suffered so much," he said.