The devastation in Myanmar from Cyclone Nargis could create a humanitarian crisis worse than that of the 2004 south Asian tsunami, the UN's secretary-general has said.

Ban Ki-Moon said on Tuesday that Myanmar had reached a "critical" point with international aid only reaching a minority of victims of the storm.

He said at a press conference in New York: "This is a critical moment for Myanmar.

"We have a functioning relief program in place, but so far we have been able to reach only about 25 percent of Myanmar's people in need."

He said Myanmar's government has allowed nine helicopters from the UN World Food Program to deliver aid to those affected by the storm.

Asean role

Ban added that he will tour the hard-hit Irrawaddy delta region as part of his visit beginning on Thursday.

"I hope I will be meeting Senior General Than Shwe and other senior government officials," he said.

Ban will co-chair a donors' conference with the Association of South-East Asian Nations (Asean) on Sunday to raise money for the relief effort in Myanmar.

John Terrett, Al Jazeera's correspondent in New York, said Ban's statement on Tuesday comes amid concerns over Asean's role in the crisis.

"Asean meets with Myanmar on a regular basis, and the feeling is that it can do a lot more to convince the ruling generals to open up to aid and aid workers," he said.

"But Asean is not a flawless organization - it is split. Nations like Indonesia and the Philippines are critical of the lack of intervention in Myanmar. Other countries like Laos, Cambodia and Thailand say that what is going on in Myanmar is an internal issue."

National mourning

Myanmar has declared three days of national mourning for the tens of thousands of victims of Cyclone Nargis, more than two weeks after the storm swept through the country.

The move is being seen as a possible indication that the country's military rulers are beginning to acknowledge the scale of the disaster and open up to foreign help.

Myanmar has agreed to allow entry to some foreign aid workers, although only from its Asian neighbors, following an Asean emergency meeting in Singapore on Monday.

Asean - of which Myanmar is a member - announced that it was setting up a task force to handle aid distribution.

The regional bloc had earlier come under criticism for failing to persuade Myanmar's ruling generals to overcome their suspicion of outsiders and allow foreign aid workers access to the country.

Asean officials said the agreement was the best approach to handling the crisis and called for the move not to be "politicized".

The first Asean teams are due to arrive in Myanmar on Wednesday, a day before Ban is expected to land in the country.

The Myanmar government says losses from the storm have exceeded $10bn.

John Holmes, the UN's top humanitarian coordinator, toured some of the worst-hit areas of the delta region on Monday before holding talks with aid groups in Yangon.

Suffering

The United Nations said the bulk of the rest of its foreign staff were still barred from the delta.

In a statement it described conditions in the region as "terrible", with hundreds of thousands of survivors suffering from hunger, disease and lack of shelter.

The official death toll from Cyclone Nargis stands at about 78,000 but aid agencies believe the number to be higher. Another 56,000 people are still missing.

Relief agencies have warned of a mounting threat of disease and say that the most vulnerable survivors will start dying soon unless they get the aid they need.

In its latest assessment, the UN said only about 500,000 of the 2.4 million storm victims had received some form of international assistance.

"It is clear that the emergency phase is set to continue for some time," it said.

The International Federation of Red Cross and Red Crescent Societies said heavy rain fell on the delta again on Monday.

While the rain could provide those able to collect some with drinking water, for many others it "simply adds to the misery as they look forward to their 18th night in often wretched conditions" it said.

"In addition, access to already relatively inaccessible locations is set to remain very difficult."

The IFRC added that it remained concerned about the distribution of relief supplies, saying "reports indicate that in most of the bigger affected townships, basic relief and food is available but much less so in the more remote areas".

Chris Webster, a spokesman for aid group World Vision, said in neighboring Thailand that "the need is still overwhelming the actual relief response".

"There's a huge challenge in the hands of the aid workers and we don't have all the people we need [in Myanmar]," he said.

PHOTO CAPTION 

A boy plays outside his home which was destroyed by Cyclone Nargis, outside Yangon May 19, 2008.

Al-Jazeera