World Bank chief Jim Yong Kim said on Wednesday international support for Jordan and Lebanon to help them cope with hosting more than 1.6 million Syrian refugees was "disappointing."
"So far the support for Jordan and also Lebanon... has been frankly disappointing. We need donor countries and all who care about peace and stability in this region to step up...," Kim told a joint news conference in Amman with Jordan's planning minister Ibrahim Seif.
"Jordan is bearing too much of a burden of a really global issue.
"This is a global problem, not just a problem for the countries of the region but for the entire world and we think it is time for other countries to really step up, make good on their promises and support this country."
Lebanon is home to more than a million refugees, while around 600,000 have fled to Jordan, and Turkey hosts another 700,000.
Syria's civil war has generated the worst refugee crisis since the Rwandan genocide of the mid-1990s, with half the population having fled their homes, including nearly three million refugees mainly sheltering in neighbouring countries.
Kim, on a regional visit, said on Monday in the Saudi city of Jeddah that the conflict in Syria has cost Lebanon $7.5 billion (5.5 billion euros).
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In December, the UN appealed for around $6.5 billion for victims of Syria's war, and $2.3 billion was pledged at a Kuwait donors' conference in January.
But UN officials have said their 2014 plan is only 25 percent funded.
"We have to make sure that in the process of accepting so many refugees this country (Jordan) which has been so stable for so long, does not suffer unnecessarily and continues to grow," said Kim.
Earlier, Kim, who met Jordan's King Abdullah II and Prime Minister Abdullah Nsur, visited the northern seven-square-kilometre (2.8-square-mile) Zaatari refugee camp, home to around 100,000 Syrians.
"I was able to visit the Zaatari refugee camp this morning and it is truly of an enormous scale but it is only a small proportion of the overall number of Syrian refuges who are here," he told reporters in Amman.
Seif said the World Bank provided Jordan last year with an easy loan of $150 million, and in March approved a $250 million loan to ease strains aggravated by the refugee influx.
"We discussed today (Wednesday) means to get more support from the World Bank for economic and investment projects in Jordan," he said.
"There is a possibility for Jordan to get $700-$800 million to support development projects, as well as $200 million to support the budget in the coming stages," he added without elaborating.