The number of Syrian refugees in Jordan is expected to triple to 1.2 million by the end of the year, the UN said Friday, lamenting a dire lack of funding for aid operations in the country.

The UN estimates that around 385,500 Syrians have already sought refuge in Jordan, including nearly a quarter of a million children.

"We expect these numbers to more than double by July and triple by December," Marixie Mercado, spokeswoman for the UN children's agency, told reporters.

The UN refugee agency, UNHCR, confirmed that it now expects the number of Syrian refugees in Jordan to surge to around 1.2 million by the end of 2013 -- equivalent to about one-fifth of Jordan's total population.

Jordan itself meanwhile says it is already hosting more than 475,000 refugees from Syria, but has said until now it expects that number to rise to just 700,000 by the end of the year.

The UN estimates that a total of around 1.2 million Syrians have fled to neighbouring countries over the past two years of spiralling bloodshed.

UNHCR said Friday it could not yet forecast the overall number of Syrian refugees by the end of 2013, or say how many it expects to see in the other main host countries, Turkey, Lebanon and Iraq.

Mercado meanwhile lamented that her agency's operations connected to the Syrian crisis were severely underfunded, stressing that the situation in Jordan was especially dire.

"The needs are rising exponentially, and we are broke," she said.

UNICEF, she said, was currently providing things like safe water, sanitation, vaccines and education in Jordan's Zaatari camp, which houses nearly 150,000 Syrian refugees.

So far, however, the agency had received only $12 million, or 19 percent of the $57 million it had appealed for to fund its Jordan operations this year, meaning it would soon need to "scale back life-saving support," Mercado said.

"In concrete terms, this means that by June, we will stop delivering 3.5 million litres of water every day to Zaatari camp. This means we won't be able to open the third school we are building at Zaatari, because we simply don't have the funds to cover the teachers' salaries, the textbooks, the furniture and the running costs of the school," she said.

Lacking funds also meant, she warned, that "UNICEF will not be able to provide water, sanitation, education, immunisation and nutrition support to two new camps slated to open in coming weeks."