UN Middle East peace envoy Robert Serry criticized the international community Monday over the failure to deliver aid promised for reconstructing Gaza, speaking on his final trip to the region and quoted by AFP.

Israel and Hamas fought a devastating 50-day war in the coastal enclave last summer which left 100,000 Gazans homeless and large swathes of the territory in ruins.

The UN and other agencies have warned failure to rehabilitate Gaza will lead to further conflict in the near future.

"Gaza is more isolated than ever, with many restrictions still in place at Israeli crossings for both goods and people and with the Rafah crossing (with Egypt) practically closed," Serry said in a statement quoted by AFP.

"Only a small percentage of the $5.4 billion pledged at the Cairo reconstruction conference (in October) has actually been disbursed. This is, frankly, unacceptable," he said.

"I urgently call on all stakeholders, including... Palestinian factions, Israel, Egypt, the international community and donors, to change their failed policies and adopt a 'Gaza first' strategy," added Serry.

More than 100,000 homes remain damaged or destroyed from the war.

Serry, who is to end his term as peace envoy next month, said there was movement towards reconstruction, but that it was too slow.

"To date, over 72,000 people have been cleared to receive construction material... and around 55,000 have actually purchased material to rebuild their homes."

But "many of those who now have access to building material lack the money to buy them or to carry out the works," he added.

UNRWA, the UN agency for Palestinian Arab refugees, has estimated that the homes of more than 96,000 Gazans were destroyed or damaged during the conflict. The high level of destruction is due to the fact that Hamas heavily entrenched its terrorist network in the civilian infrastructure of Gaza.

In late January, UNRWA said that it cannot afford to repair Gaza homes damaged in last year's war with Israel - because donors have failed to live up to their pledges to pay.

"The agency has exhausted all funding to support repairs and rental subsidies," it said.

"$5.4 billion was pledged at the Cairo (aid) conference last October and virtually none of it has reached Gaza. This is distressing and unacceptable. It is unclear why this funding has not been forthcoming," added the UN agency.

A Hamas official warned recently that the coastal territory could become a breeding ground for extremism unless promised reconstruction is accelerated.