Business leaders gathered at a Rio+20 conference Monday pledged sustainable policies and joined a call for world leaders to usher in "a green industrial revolution" to save the planet.

Two days before a UN summit on sustainable development opens here, 1,200 CEOs wrapped up a four-day meeting with more than 150 voluntary commitments to greater energy efficiency, reforestation and a lower carbon footprint and other green policies.

Forty-five chief executives vowed to make water security a strategic priority and called for decisive action by governments.

"Problems related to water availability, quality and sanitation are undermining development in many regions of the world -- exacting an enormous human cost while also undermining critical life-giving ecosystems," they said.

Signatories include chiefs of global companies such as Pepsico, Coca Cola, Nestle, Saint-Gobain, Royal Dutch Shell, Akzo Nobel, Bayer, Heineken and Pernod Ricard.

Roughly 800 million people around the world lack access to safe drinking water, and 2.5 billion lack basic sanitation, according to the United Nations.

The UN Global Compact, the sponsor of the business forum, said it tallied more than 150 "time-bound, measurable commitments" on which companies are required to report annually.

The commitments centered on the forum's six core themes: energy and climate, water and ecosystems, agriculture and food, social development, urbanization and cities, economy and financing.

US chemicals giant Dupont pledged $10 billion to research and development and announced plans to launch 4,000 new products by late 2020 to produce more food, enhance nutrition and curb food waste.

US technology titan Microsoft vowed to achieve net zero emissions for its data centers, software development centers, software development labs, offices and employee air travel by boosting energy efficiency and buying renewable energy.

Global clothing retailer H&M said it would upgrade to 100 percent sustainable cotton -- organic or recycled -- in its cotton garments while US sporstwear giant Nike set a target of zero discharge of hazardous chemicals across its entire supply chain by 2020.

And South Africa's state-owned utility Eskom and US Duke Energy pledged to assist the development of an electrification roadmap to ensure 500 million people across Africa and developing countries have access to energy by 2025.

The Global Compact, which rejects charges by critics that it is a mere marketing tool for big business, said the commitments will serve as a testing ground.

Meanwhile, former British premier Tony Blair, in a speech screened at the Rio+20 conference, joined other statesmen and corporate chiefs in appealing to world leaders to usher in a "green industrial revolution".

"By the end of the decade, the low carbon market could triple in value to over US$2 trillion," said the signatories of an open letter published on the eve of the G20 and Rio+20 summits.

The letter called for a coordinated policy shift to save the world economy and the climate.

"At a time when government and business leaders everywhere are calling for strategies that deliver growth, we have an historic opportunity before us to lead the world out of recession and into a more stable, sustainable future," the signatories said.

They backed the launch in Rio of a Clean Revolution campaign, a major initiative by the Climate Group and other public and private sector partners for a "green growth" push out of global recession.

The Climate Group works with business and governments around the world to promote clean technologies and policies, with the aim of expanding clean technology markets and reducing global greenhouse gas emissions.

The three-day Rio+20 summit, coming 20 years after the first Earth Summit is expected to bring together 130 world leaders for a fresh appraisal of the health of the planet. But US President Barack Obama, British Prime Minister David Cameron and German Chancellor Angela Merkel will be absent.