Microsoft founder Bill Gates is pouring millions of dollars into a global effort to cut smoking.

Mr Gates is teaming up with fellow billionaire philanthropist Michael Bloomberg, the mayor of New York, to fight tobacco use in developing countries, where it is most entrenched.

The two men, with a combined worth of more than £35 billion, are donating a total of £189 million ($375 million)  to the campaign.

Campaigner: Bill Gates speaks at the launch of his joint effort with New York mayor Michael Bloomberg

Two thirds are coming from Mr Bloomberg and a third is being donated by Mr Gates.

The money will support projects that raise tobacco taxes, help smokers quit, ban tobacco advertising and protect non-smokers from exposure to smoke, their foundations said today.

It will also aid efforts to track tobacco use and better understand tobacco control strategies.

There are more than a billion smokers worldwide.

'Bill and I want to highlight the enormity of this problem and catalyse a global movement of governments and civil society to stop the tobacco epidemic,' the New York mayor said in a statement.

Mr Bloomberg, who built his fortune from the financial information company he founded in the 1980s, is adding to an anti-smoking initiative he funded with $125 million (£63 million) in 2006.

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Target: Gates hopes to curb tobacco use in countries such as China, where this four-year-old was taught to smoke by factory workers

When he announced that initiative, he said smoking was a public health issue largely ignored by philanthropists and he hoped to draw more attention to it from other major foundations.

His money goes toward tobacco-fighting campaigns in low- and middle-income countries, particularly China, India, Indonesia, Russia and Bangladesh.

The Bloomberg foundation is also conducting a survey to better understand smoking in those countries.

Mr Gates said today that $24 million of his gift will go directly toward efforts that are already under way by Mr Bloomberg's foundation.

The remaining money will be used by the Bill & Melinda Gates Foundation - run with his wife - to begin its own anti-tobacco work, including preventing tobacco use from increasing in Africa.

'Tobacco-caused diseases have emerged as one of the greatest health challenges facing developing countries,' Mr Gates said today.

'The good news is, we know what it takes to save millions of lives, and where efforts exist, they are working.'

Mr Bloomberg, a former smoker who quit about 30 years ago, has crusaded against smoking as mayor. In his first term he banned smoking in bars and restaurants and his health department has an aggressive, on-going campaign to help New Yorkers kick the habit.