UNITED NATIONS - The UN's top humanitarian official urged the Myanmar authorities on Wednesday to allow more international aid workers into the affected area in the delta outside Yangon, the country's largest city.

Speaking to reporters at a press conference at the UN Headquarters, Under-Secretary-General for Humanitarian Affairs John Holmes said that opening up the area as much and as soon as possible could make a huge difference.

"It's perfectly obvious I think to everyone that the national resources that they have are not adequate to cope with the problems," he said.

He said that, in a "selective opening up to international staff" the government had invited its immediate neighbors China, Bangladesh, Thailand and India to send 160 international workers to join the relief effort.

Holmes added that around 550,000 people had now gathered in rudimentary camps scattered through the Irrawaddy delta area.

Increasing quantities of supplies were reaching Myanmar, he said, though he described the current level of aid as "inadequate. "

Between 25 and 30 special flights had arrived in Yangon in the past few days, in addition to regular airline flights which have also been ferrying in relief supplies. 25,000 tarpaulins have been distributed to households, with 50,000 more on the way.

Holmes said that aid agencies were aiming to cover at least 200, 000 households.