A U.N. agency on Tuesday appealed to Israel to ensure unfettered access for humanitarian aid to the Gaza Strip.

Mattias Burchard, a spokesman for the UN Relief and Works Agency for Palestine Refugees in the Near East (UNRWA), said there were severe backlogs in deliveries into the territory.

"UNRWA appeals to Israel to continue to allow the much needed essentials for life to enter unfettered," Burchard told a press conference.

"Any renewed blockage will again bring the (Gaza) Strip to the brink of catastrophe," he said.

He voiced grave concerns about Gaza residents' access to clean water, saying chlorine supplies for water purification was expected to run out in 15 days while a shortage of power prevented water from being pumped to high-rise buildings.

The UNRWA was running out of aid materials in Gaza, said the spokesman, appealing for urgent international aid.

Israel had closed Gaza's borders and sent tanks, troops, gunboats and aircraft to raid the Gaza Strip over the past days in a bid to press Palestinian militants to free a captured Israeli soldier.

The Palestinian militants have demanded that Israel release Palestinian prisoners in exchange for the soldier and set Tuesday as the deadline.

However, Israel has rejected the ultimatum, saying it would not give in to blackmails.

Source: Xinhua