Pope Francis appealed for better preservation of water at his weekly audience at the Vatican on Wednesday, as a major conference on the issue got underway in New York.

"I pray for a good result" from the UN meeting "and hope this important event will accelerate initiatives to help those who suffer from the shortage of water, this basic resource", the 86-year-old pontiff said.

"Water cannot be the object of waste or abuse, or a reason for wars, but must be preserved for the benefit of us and for future generations."

Co-hosted by the governments of Tajikistan and the Netherlands, the UN Water Conference will gather some 6,500 participants, including around a hundred ministers and a dozen heads of state and government.

In a report published ahead of its opening, the UN warned water is increasingly at risk around the world due to "vampiric overconsumption and overdevelopment".