The world is facing a "global water crisis" due to population growth, socio-economic development and changing consumption patterns, the United Nations has warned.

Globally, 2 billion people do not have safe drinking water and 3.6 billion lack access to safely managed sanitation, according to a UNESCO report released ahead of the U.N. Water Conference in New York on Wednesday.

"There is an urgent need to establish strong international mechanisms to prevent the global water crisis from spiraling out of control," said UNESCO Director-General Audrey Azoulay.

"Water is our common future, and it is essential to act together to share it equitably and manage it sustainably."

The global urban population facing water scarcity is projected to potentially double from 930 million in 2016 to between 1.7 and 2.4 billion people, in 2050.

The rising incidence of extreme and prolonged droughts is also stressing ecosystems, with dire consequences for both plant and animal species, the report said.

Editor-in-chief of the report Richard Connor said building partnerships and cooperation were key to realizing human rights to water and overcoming existing challenges.

"If we don’t address it, there definitely will be a global crisis," he said.

The U.N. Water Conference, co-hosted by the Netherlands and Tajikistan, will take place over three days in New York. It is the first U.N. event of its kind focussing entirely on water policy in nearly 50 years.