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UNITED NATIONS, May 14 (Reuters) - The United Nations on Wednesday raised its estimate for the number of victims in need of aid in cyclone-ravaged Myanmar and again urged the government to remove all restrictions on getting aid to them.

U.N. humanitarian affairs chief John Holmes told reporters that there were now between 1.6-2.5 million people who were "severely affected" by Cyclone Nargis and urgently needed aid, up from a previous estimate of at least 1.5 million people.

The cyclone swept through Myanmar's heavily populated Irrawaddy delta rice bowl in early May, leaving 100,000 people or more dead or missing, and many of the survivors homeless and hungry, according to the United Nations.

Holmes said that there had been slight improvements in access for foreign aid workers with expertise that the authorities of Myanmar, formerly know as Burma, lacked.

"We have seen one or two small signs of progress in some areas," he said, but added that it was "by no means adequate to the task."

International aid has amounted to little more than a trickle as Myanmar's generals resist international efforts to open the floodgates to foreign workers and their operations and equipment.

Holmes was asked if the United Nations might have to consider air drops to get food and other aid to cyclone victims who have not been helped. He said it was not an ideal form of distributing aid but might become an option.

"It is something that could be contemplated," he said, adding that if barriers to aid workers were not lifted "one might have to look at it."

He also warned that epidemics of diseases like cholera, malaria and measles "can break out at anytime now."

(Reporting by Louis Charbonneau, editing by Sandra Maler)

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