The director of the United Nations' humanitarian operations is warning that some of Syria's neighbors are at their "breaking point," caught between a sense of duty to keep their borders open to refugees and a responsibility to their own citizens.

John Ging said Wednesday that Lebanon, Turkey and Jordan likely will have the refugees "for many years to come." About 3.3 million people have fled Syria.

His remarks come a day after Jordan and Lebanon told an international conference that the influx is straining their resources and threatening political stability.

In the case of Lebanon, refugees have made for a 25 percent increase in the population.

Ging urged more international funding to help ease the burden. He said a $3.7 billion appeal for the Syrian refugee crisis is just 52 percent funded.