* Bombing hits the enclave's already poor infrastructure
* Foreign donors already distracted by other crises
* Resident mourn lost homes in wrecked neighbourhoods
By Nidal al-Mughrabi and Noah Browning
GAZA, July 25 (Reuters) - As the United States and regional powers strive for a ceasefire between Israel and Gaza militants, the impoverished enclave faces a daunting recovery, such is the scale of damage after almost three weeks of fighting.
Israeli artillery has shredded entire neighbourhoods and air strikes have pounded the scant infrastructure that barely kept the crowded strip of 1.8 million people running even in peacetime.
In 2012 the United Nations had already recommended urgent action to improve basic services for Gaza's mushrooming population or the place would be uninhabitable by 2020.
This month's fighting can only have made that warning more pressing. At least 2,655 homes have been totally or severely damaged, while another 3,175 are damaged but not beyond use, the U.N. said.
Bombs have lashed 116 schools and 18 health centres, stadiums, playgrounds, mosques, roads, phone towers, water lines, sewage treatment plants and police stations.
The cost of rebuilding Gaza homes destroyed so far in Israeli bombing amounts to $800 million - the whole of Gaza's annual budget - the Palestinian housing minister told Reuters.
Mufeed Al-Hasayna said he could not yet calculate the damage to public buildings or infrastructure, adding that it had received precious little foreign aid to help recovery after past wars.
"We cannot make a definite estimate under fire ... Once the war is over, the ministry plans to call on all the countries of the world to assist in the rebuilding of Gaza," he told Reuters.
"We want real aid and not words. (At the end of another war in 2009) donors promised nearly $5 billion and not a penny arrived. We want real help for Gaza this time," added Husayna, a political independent.
Gaza medics say 816 Palestinians have been killed, most of them civilians, and over 5,000 have been wounded. On the Israeli side, 32 soldiers and three civilians have been killed. But this human tragedy has to compete with others to open the world's purse strings.
The Gaza head of UNRWA, the largest U.N. agency operating there, warned that donors' attention had already been drifting from the seemingly intractable Palestinian-Israeli conflict.
"It's difficult to sustain emergency funding over time. We're victims of the competition, and frankly there's a level of humanitarian need unprecedented in modern history in the world, with the situations in Mali, the Phillipines, South Sudan, Syria and Iraq," Robert Turner told Reuters.
"And we're all competing for the same funds," he said.
Cash is also painfully tight for the Hamas government. An Israeli-Egyptian blockade of the strip led to a $500 million shortfall in its proposed annual budget.
The group, which is blacklisted as a terrorist organisation by its two neighbours and many Western countries, hopes to win the opening of its border crossing with Egypt to goods and people in a truce.
Hamas in April struck a unity deal with Palestinian rivals in the occupied West Bank, but the Western-backed Palestinian Authority there also struggles with a severe shortfall and despite the reconciliation pact has yet to exercise its authority in Gaza.
Whole suburbs of border areas lying within a 3-kilometre buffer area on Gaza's border lie abandoned, sealed into the combat between the guerrillas and the Israel Defence Forces.
The area of the main power plant was hit by two missiles, leaving four-fifths of Gazans with only four hours of power a day. The sewerage and water infrastructure to two-thirds of Gaza residents have been affected by the bombing, leaving many without water and others wading through streets mired in sewage, according to British charity Oxfam.
According to the Israeli media, the Israeli air force dropped about 3,000 tons of explosives on the Gaza Strip in the first 15 days of the conflict, including 120 tons in the border town of Shejaia alone, once home to 100,000 residents, which was the centre of fierce battles when an Israeli infantry push began on Saturday.
The fighting led to an exodus that has put intense strain on the cash-strapped U.N. and neighbouring Gaza areas.
Over 140,000 refugees from affected areas have fled to schools run by the U.N.'s main agency in Gaza, UNRWA, while thousands of others have moved in with relatives or friends.
From a loudspeaker in a mosque in central Gaza, a cleric urged neighbours to provide clothes and blankets to needy refugees.
Owners of supermarkets and vegetable stands said their stocks were put under stain by the influx of outsiders.
"There's no bread, no soup, and, sorry, no water bottles. Our brothers from Shejaia took it all," said one supermarket owner in central Gaza.
In the courtyard of Gaza's main Shifa hospital, relatives of patients mixed with refugees too afraid to return to neighbourhoods now turned to warzones.
Um Ahmed Hassan covered her face in shame as she pointed to her two children, aged five and seven, sleeping on a nearby patch of grass - she had no blankets to cover them and hoped that her husband would return bringing word that a relative or friend had agreed to take them in.
From local news footage from their street in Shujaia, they could see their house and those next to it had been destroyed.
"Fadi and Ali each had his own room, his own bed and cupboard," she said weeping.
"At this time of day they would be playing in their rooms, in the house where they were born and grew up. Our house." (Editing by Will Waterman)