CAIRO, June 21 (Reuters/Marwa Awad) - Nothing short of the full lifting of Israel's blockade on Gaza would allow the territory to be rebuilt, the UN agency responsible for Palestinian refugees said on Monday, a day after Israel said it would ease its siege.

Israel, which sealed off the coastal territory to prevent its Hamas foes from arming, is under international pressure to lift the blockade after its forces killed nine people in an assault on an aid flotilla on May 31.

Under the blockade's previous rules, any item that was not explicitly permitted was banned. Israel says it will now allow items to enter Gaza unless they are on a list of banned items, including weapons and materials that can be used to make them.

However, critics say the new rules could still make it difficult to import building materials to rehabilitate the territory, damaged by war in 2008-09.

We need to have the blockade fully lifted, said spokesman Christopher Gunness of UNRWA, the United Nations relief agency that looks after Palestinian refugees. He spoke to Reuters on the sidelines of a conference in Cairo.

The Israeli strategy is to make the international community talk about a bag of cement here, a project there. We need full unfettered access through all the crossings.

International donors at a conference in Egypt pledged $2.8 billion to rebuild Gaza after the war, but the blockade has hampered the inflow of building supplies.

Gunness said he was not confident that the new Israeli system would resolve the difficulties UNRWA has faced determining what can get through the blockade.

The list of restricted goods is a moving target. We are never told this is banned and that is banned, he said. Israel's blockade became a blockade against the UN

Gunness said Israel must open the Karni cargo terminal north of Gaza, which is large enough to allow industrial-scale cargoes of cement, building materials and aid. Instead, trucks are routed to a narrower crossing.