United Nations Secretary-General Ban Ki-Moon on Tuesday warned that by 2030, half the people on Earth would be living under "water stress," a measure defined as less than 1,700 cubic meters of water available per person per year, unless action was taken.

Addressing the Budapest Water Summit with Hungarian President Janos Ader, Ban noted that while water was a government priority, no government could handle the work alone.

We "need the full engagement of all actors, communities, societies," he said.

Ban announced a conference devoted exclusively to climate change would be held next September during the UN General Assembly and called for representation from countries at the highest level.

Addressing the gathering, UNESCO Director-General Irina Bokova noted that nearly one billion people lacked clean drinking water and billion and a half did not have access to basic health care.

Other speakers included WHO Director-General Margaret Chan, World Meteorological Organization Secretary-General Michel Jarraud, Food and Agriculture Organization Director-General Jose Graziano da Silva, among other leaders of governments and international organizations.

The summit, being held under the auspices of the UN and the World Water Council, is calling for designing practical, accessible and affordable measures to secure future supplies.

The summit seeks consensus on water and sanitation policy goals with the aim of making concrete recommendations for sustainable development goals (SDG) to the next UN General Assembly.

The summit will include forums with business leaders, youth and scientists and civil society before concluding on Friday.