SINGAPORE, July 21, 2008 (AFP) - Rebuilding Myanmar's cyclone-devastated south and bringing aid to millions of survivors will cost one billion dollars over the next three years, the United Nations and ASEAN said Monday.

A joint report by the UN, the 10-member Southeast Asian bloc and the Myanmar government said the priorities were providing food, restoring agriculture and basic services, and helping communities rebuild and recover their livelihoods.

'Recovery needs... are estimated at just over a total of one billion dollars over the next three years,' it said.

The report outlined the scale of Myanmar's worst ever disaster, which damaged or destroyed 800,000 homes, flooded 600,000 hectares of agricultural land and left 138,000 people dead or missing.

Some 4,000 schools were wiped out in the May 2-3 cyclone, which drove a massive storm surge into the coast, and about 75 percent of hospitals and clinics were destroyed or badly damaged.

By mid-June, more than half of the cyclone survivors had no more than one day of food stocks in hand, leaving them extremely vulnerable, the report said.

'While significant progress has been made to date, we are still in the relief phase of this aid operation,' said UN humanitarian chief John Holmes.

Endorsing the report as a 'credible and comprehensive assessment,' he said he hoped it would encourage the international community to fund the massive recovery programme.

'A key request put forward by donors... was that there should be full access and that there should be a credible assessment on the table. I think both these things are now in place,' he said.

Myanmar's ruling generals drew international outrage by refusing to allow a foreign-led aid response in the immediate aftermath of Cyclone Nargis.

The Association of Southeast Asian Nations (ASEAN) was initially criticised for not doing enough to pressure its military-run member to open its doors.

But the bloc's work since then to bridge the gap between the secretive junta and the international aid community, and send in hundreds of foreign experts, has won over many of the critics.

ASEAN Secretary-General Surin Pitsuwan said the total cost of Cyclone Nargis was about four billion dollars -- 1.7 billion dollars in damage and 2.3 billion dollars from lost income of those affected.

'We have begun to wipe some tears, soothe some aching hearts, we have relieved some suffering, but not all,' he said.

'The task ahead is clearly enormous and will clearly take a lot of time, a lot of resources from government and international community helping out as well.'

Singapore's Prime Minister Lee Hsien Loong said the crisis had challenged ASEAN's unity, but that the bloc passed the test by successfully leading the international relief effort.

'Just as we could not ignore political developments in Myanmar, neither could we stand aside from this humanitarian crisis when so many lives had been lost and many more remained at risk,' he said at the group's annual talks of foreign ministers.

'While many difficulties still lie ahead, ASEAN played an important role in bridging the gap of trust between the Myanmar government and international organisations like the United Nations and World Bank.'

The tripartite process with the UN and the Myanmar junta was 'far from perfect,' but the situation was clearly better than if ASEAN had not intervened to persuade the ruling generals to cooperate, he said.

With many of the estimated two million victims still in urgent need of assistance, Lee said that much remained to be done and that only the international community was able to carry out the enormous task.