By Olivia Rondonuwu and Ed Davies

JAKARTA, June 27 (Reuters) - The impact of cyclone Nargis on Myanmar may not be as dire as initial assessments, but its ruling junta will still need to be coaxed into keeping vital aid flowing in, the ASEAN secretary general said on Friday.

The 10-nation Southeast Asian grouping played a key mediating role in getting Myanmar's military leaders to open up to foreign aid, ASEAN Secretary General Surin Pitsuwan said.

"I think a humanitarian space has been opened and I think the challenge is to maintain it and the challenge is to widen it a little bit if possible," Surin said in an interview.

Nargis slammed into the densely populated Irrawaddy delta on May 2, leaving more than 138,000 people dead or missing and 2.4 million destitute.

Despite the magnitude of the disaster, the reclusive junta has been reluctant to admit outside aid operations, particularly from Western donors.

The former Thai foreign minister, who had just returned from a visit to Myanmar, said despite "heartbreaking" scenes of devastation people were getting back on their feet.

"The situation is not as bleak as it was feared, partly because these people were resilient," he said, adding that feared disease pandemics had also not occurred so far.

The Association of Southeast Asian Nations, headquartered in Jakarta, has often been criticised for being a toothless organisation, but Surin said the Myanmar disaster was a "historic moment for ASEAN" to show it could lead an international humanitarian effort.

He said many in the former Burma's "rice bowl" had lost water buffaloes and since the sea surge had salinated a lot of land many people did not have enough or the right type of rice seeds.

A joint assessment team ASEAN is heading had been given good access by Myanmar across the delta area, Surin said.

They found villages where no aid had been delivered and "they called in WFP (the U.N.'s World Food Programme). Help was ferried in in the next 36 hours," he said.

Asked if ASEAN should have put more pressure on Myanmar, Surin said despite the length of time it had taken, the junta had followed up what the Southeast Asian body had recommended.

"Right now I guess we are working on the transitional phase between relief and rescue into early recovery," he added.

He said that, as was the case of the Indian Ocean tsunami in 2004, the aid effort after Cyclone Nargis would be needed for years.

"I think the challenge is for us to work together if the world is ready and if it's what the leadership in Myanmar wants we can rehabilitate that region into the traditional rice bowl." (Editing by Jerry Norton)

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