Microsoft founder Bill Gates and New York Mayor Michael Bloomberg are pooling their piles of money to pour $375 million into a global effort to cut smoking.

The billionaire philanthropists, who have a combined worth of more than $70 billion, said Wednesday that the money will help efforts in developing countries where tobacco use is highest. There are more than 1 billion smokers worldwide.

The $250 million from Bloomberg and $125 million from Gates will support projects that raise tobacco taxes, help smokers quit, ban tobacco advertising and protect nonsmokers from exposure to smoke, their foundations said. It will also aid efforts to track tobacco use and better understand tobacco control strategies.

"Bill and I want to highlight the enormity of this problem and catalyze a global movement of governments and civil society to stop the tobacco epidemic," Bloomberg said in a statement.

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 in 2006.

That money goes toward tobacco-fighting campaigns in low- and middle-income countries, most specifically China, India, Indonesia, Russia and Bangladesh. The Bloomberg foundation is also conducting a survey to better understand smoking in those countries.

When Bloomberg first announced that $125 million gift, he said at the time that he believed smoking was a public health issue that was largely ignored by philanthropists. He said he hoped publicizing it would bring more attention from other major foundations.

Gates said Wednesday that $24 million of his gift will go directly toward Bloomberg's efforts that are already underway.

The remaining money will be used by his foundation 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," Gates said in a statement. "The good news is, we know what it takes to save millions of lives, and where efforts exist, they are working."

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, ongoing campaign to help New Yorkers kick the habit.