San Francisco has banned the purchase of bottled water by city and county governments. Mayor Gavin Newsom's order took effect this month and will include water coolers in December, allowing purchases only when drinking water is unsafe or difficult to access.

Newsom said more than a billion bottles go to California landfills yearly, and the move will help curb global warming while saving US$500,000 annually.

The city says bottled water is no better than tap water, but the Virginia-based International Bottled Water Association (IBWA) said this encourages a "confusing debate," since city employees will use point-of-use filtration systems in place of bottled water coolers.

The IBWA said plastic bottles are among the most recycled packaging and officials should instead focus on improving recycling rates.

The move comes only days after the City of New York launched an advertising campaign to persuade its people to give up bottled drinks and consume tap water instead to help protect the environment.

The ads in subways and buses promote the city's tap water as "delicious" and more environmentally friendly than bottled water. The city environmental protection commissioner says bottled water takes more energy to produce and transport than tap water does.

City officials say their campaign will save people money, and reduce waste.