Britain is set to award £19 million in aid for refugees in Gaza.
The money, to be spent on healthcare, education and other services, will be announced by International Development Secretary Andrew Mitchell on Sunday.
It will go to the UN Relief and Works Agency (UNRWA), on which about 70% of Gazans rely to meet their basic needs.
The support comes amid heightened international concern about Israel's blockade of Gaza after the violent confrontation on an aid ship this week.
But the money is part of a five-year £100 million funding arrangement with the UNRWA that was entered into in 2006.
Mr Mitchell, who has confirmed the latest tranche of support, reiterated the Government's calls for Israel to allow aid into Gaza.
"The humanitarian situation in Gaza is both unacceptable and unsustainable," he said.
"The UK is committed to helping those people affected by this crisis and that is why I am today providing £19 million to help meet their most basic needs.
"There is an immediate need for unfettered access to Gaza if the humanitarian situation is to be improved, to allow the economy to get back on its feet, and to give the young people of Gaza the prospect of a better future.
"I call on the government of Israel to open the crossings to help end this humanitarian crisis."
