The world is going to face a pandemic of the bird flu strain lethal to humans and Thailand is the only nation in South and Southeast Asia ready to deal with it, the World Health Organization (WHO) warned on Wednesday.

WHO officials said the virus could mutate into a form that could pass easily from one human to another, making it easier for it to spread rapidly across great distances and kill between one million and seven million people worldwide.

"We may be at almost the last stage before the pandemic virus may emerge," Dr. Jai P. Narain, Director of WHO´s communicable diseases department told a news conference on the sidelines of a Southeast Asia health summit in the Sri Lankan capital.

"Whether the avian influenza pandemic will occur, that is not the question any more, (but) as to when the pandemic will occur," he added.

"So far there is only one country in Southeast Asia with a pandemic preparedness plan...Thailand...They have a stockpile of antiviral drugs," Narain said. "At the same time we are in dialogue with our member countries. We are in the process of preparing this pandemic preparedness plan."

The deadly bird flu virus, now feared to be heading for Europe, killed one person in Vietnam last week, taking the number of deaths in Asia from the disease to 63.

The death took Vietnam´s bird flu death toll to 44, with 23 of the victims dying since the virus returned in December 2004, after sweeping through much of Asia in late 2003.

It has also killed at least 12 people in Thailand, 4 in Cambodia, 3 in Indonesia and has struck 6 Russian regions and Kazakhstan, causing the deaths of nearly 14,000 fowl.

Narain said migrating birds posed a serious risk of spreading avian flu around the world and Asia was very vulnerable as winter approaches.

"It is no longer poultry. We are concerned about a whole range of bird species," Narain said.

"The virus has been detected in migratory birds in some former Soviet states where the these birds traditionally fly towards Asia to escape the cold winter months," he added.