Not merely content to ban smoking in bars, restaurants and stadiums here, New York City Mayor Bloomberg is joining with Bill Gates to spread his anti-smoking crusade around the world.

The multibillionaire pair have announced a joint $500million campaign to persuade smokers in Asia, Africa and across the globe to put down their cigarettes.

"There are now 300,000 fewer smokers in New York City than there were six years ago," Bloomberg said, crediting his ban on smoking in bars among other anti-smoking efforts.

"The progress we've achieved here in New York helped convince me to take on the global initiative because I believe that a world in which everyone is aware of the destructiveness of tobacco and empowered to avoid it is within our reach."

Bloomberg and Gates, have a combined net worth of $70 billion.