He said the United Nations Relief and Works Agency for Palestine Refugees needs around USD 415 million, of which USD 250 million would fund its cash program which provides cash distributions for roughly half a million Palestinian refugees affected by the war in Syria.
Gunness spoke to The Associated Press from Kuwait, where an international conference will take place Tuesday to raise funds for humanitarian operations in Syria.
"It will be devastating," he added. "This is literally a lifeline. It is quite literally a matter of life and death."
More than 95 percent of Palestinian refugees from Syria rely on UNRWA assistance, particularly the cash distributions due to high unemployment caused by the Syrian civil war, now in its fifth year.
The agency's relief reaches some 475,000 Palestinian refugees still residing in Syria, with another 45,000 in Lebanon and 15,000 in Jordan where many have fled.