New York  - The United Nations called Friday for the injection of 15 billion dollars a year into the global water market to meet daily water needs of billions of people as it marks World Water Day on Sunday.

March 22 each year is dedicated to water, a commodity called "the most precious natural resource" by UN Secretary General Ban Ki-moon.

"More than ever we need to work together to use it wisely," Ban said in a prepared message for World Water Day.

He said water is becoming scarce because climate change is drying up glaciers, rainfall has become less predictable and floods and droughts are more extreme.

The UN Environment Programme (UNEP) said investing 15 billion dollars a year in the market for water supply, sanitation and efficiency could halve the more than 1 billion people expected to be without sustainable access to water by 2015.

UNEP said the water market is worth over 250 billion dollars a year, growing to 660 billion dollars by 2020.

This week, UNEP executive director Achim Steiner urged the world's 20 most advanced economies to discuss investing 1 per cent of global gross domestic product - about 750 billion dollars - into five sectors to build an environmentally sustainable global economy, one of which is water.

G-20 leaders will meet in London April 2.

UNEP said if such an amount is set aside, it could finance a "Global Green New Deal," drawing on the idea of the New Deal launched by US president Franklin D Roosevelt to help put an end to the Great Depression in the 1930s.

The world's largest economies are to spend up to 3 trillion dollars in stimulus packages to revive the world economy in deep recession.

UNEP said the United States plans to spend 4 billion dollars on clean water infrastructure and 2 billion dollars for drinking water from its stimulus money.

South Korea's stimulus includes nearly 12 billion dollars for improvements of four rivers and the chance to generate 16,000 jobs.

Australia's stimulus includes investing in the Murray-Darling river system, which provides water for half of the country's agriculture, UNEP said. (dpa)