GENEVA (AP) _ Smoking will be banned starting Tuesday at the Geneva headquarters of the World Health Organization, one year after a WHO report described the habit as the ''major avoidable cause of ill health.''

A statement said the ban, marking World Health Day, was intended to set an example of ensuring a smoke-free environment in public places.

WHO spokesman Gino Levi said non-smokers make up more than two-thirds of the approximately 1,300 staff members at headquarters. The ban will apply to all offices except a small eighth-floor lounge with capacity of fewer than 100 people.

A 1986 WHO report estimated that tobacco use caused at least 1 million premature deaths each year worldwide.