(Adds comments on level 6 alert, drugs, World Health Assembly)

GENEVA, May 2 (Reuters) - There has not yet been a sustained spread of H1N1 flu outside North America but a pandemic is still "imminent", a World Health Organisation official said on Saturday.

Michael Ryan, WHO Director of Global Alert and Response, said it remained probable that the alert level would be raised from its current level of 5 to the top of the 6-stage scale.

"We have no evidence of sustained community spread outside of North America," he told a news briefing at the U.N. agency's Geneva headquarters. "We are still at Phase 5.

"At the present time I would still propose that a pandemic is imminent, because we are seeing the disease spread," Ryan said. "At this point we have to expect that phase 6 will be reached, we have to hope that it is not reached."

WHO Director-General Margaret Chan raised the pandemic alert level from 4 to 5 on Wednesday, a move that triggered pharmaceutical efforts to produce antiviral drugs and find a vaccine to fight the new strain widely known as swine flu.

Level 5 indicates that a pandemic is "imminent".

Ryan said the WHO would send more than 2 million treatment courses of antiviral drugs to the world's poorest countries to help them prepare for the continued spread of the virus that could expose HIV-positive patients to extra risks.

While the WHO has warned against major public events and gatherings in flu-affected areas, it still plans to go ahead with its annual World Health Assembly this month, which will draw health ministers and officials worldwide to Geneva.

"There are no plans to cancel or postpone or curtail or limit the World Health Assembly," Ryan said. (Reporting by Laura MacInnis; editing by Robert Woodward)