HONG KONG, Nov 29: Up to 100 million people could die within weeks if a bird flu pandemic broke out, a senior World Health Organisation official warned on Monday as he urged nations to make urgent preparations to mitigate its spread.

A global outbreak is almost certain and even wide scale vaccination programmes would not be enough to halt its inexorable spread, WHO director for the Western Pacific Shigeru Omi said in Hong Kong.

"The most conservative estimate is that 7-10 million people would die, but the maximum range will be more - 50 million or even in the worst case 100 million people," Mr Omi said in his starkest warning yet of the potential peril from a mutation of avian flu to a form that could be transmitted by humans.

"It will come," he said during a flying visit to the city where the H5N1 flu strain first mutated into a strain lethal to humans. He said it was impossible to predict when a pandemic would happen but said it would not take long to reach all corners of the globe.

"Before it would have taken a year to spread around the world but thanks to globalization it will take just weeks. "If we are not prepared the consequences will be serious."

Avian flu, he said, appeared to be entrenched in Asia following two huge outbreaks throughout the region earlier this year that killed 32 people in Vietnam and Thailand.

Believed to be transmitted through contact with bird droppings, he said the speed of the virus's spread and its adaptation to a form that can be carried by pigs and cats had shown conditions were ripe for a devastating pandemic.

"The level of transmission at the moment in unprecedented historically," he added. "History has told us that on average every 30 years, at least, a pandemic will occur. The next one is due - some would say it is overdue."

Mr Omi's bleak assessment followed a summit of world health leaders in Bangkok last week in which guidelines were laid down for national preparation plans to reduce the effects of a possible pandemic in the coming winter. -AFP