South-east Asian countries have offered to lead an international “mercy coalition” to help the estimated 1.5m survivors of Cyclone Nargis in an effort to address Burma’s mounting humanitarian crisis.

Surin Pitsuwan, secretary-general of the Association of South-East Asian Nations, said UN representatives had given their nod of approval for a plan backed by Burma to let Asean coordinate the aid effort. Burma is a member of the 10-nation grouping.

Mr Surin, who flew to the United States on Tuesday to meet Robert Zoellick, president of the World Bank, to confirm his organisation’s participation, said the Burmese junta asked for Asean to lead efforts because of the regime’s “lingering suspicions” of westerners.

“But we are beginning to see a ray of hope at the end of a long dark tunnel”, he told the Financial Times.

UN officials could not immediately be reached to confirm Mr Surin’s claim.

After blocking most international aid for a week, Rangoon has started to accept increasing amounts of foreign relief supplies for the victims of cyclone Nargis which struck on May 2. But aid agencies say only a fraction of the victims’ needs are being met and complain that western aid workers are not being given visas.

The military junta raised the official death toll to more than 32,000 on Tuesday and has said a further 30,000 people are missing. The UN has put the likely death toll at more than 100,000 while aid agencies have said that up to 1.5m people have been left homeless or are suffering shortages of basic supplies.

Mr Surin said the first Asean rapid assessment team entered Burma on Monday, two more were scheduled to follow on Tuesday and the secretariat staff are working round-the-clock to coordinate the response. The Asean secretariat is based in Jakarta.

“This is the beginning of a long and difficult process to deliver immediate relief, medium term rehabilitation and long term reconstruction,” he said. “We expect support, contributions and cooperation from all relevant agencies for their advice, expertise and resources.”

Singapore, Thailand, Malaysia, Indonesia, the Philippines, Brunei, the UN’s Office for the Coordination of Humanitarian Affairs and the World Bank will be the coalition’s initial members, Mr Surin said.

Asean foreign ministers are expected to formally approve the initiative when they meet in Singapore on May 19.

Mr Surin said meeting this challenge would be a “defining moment for Asean” after decades of largely ineffectual leadership.

Politicians and analysts around the region have criticised the organisation for failing to persuade Burma to accept international aid as Indonesia and Thailand did after the 2004 tsunami.