US Secretary of State Hillary Clinton warned Thursday of the risk of terrorism, political instability and conflict over competition for scarce water supplies worldwide over the next few decades.

Clinton highlighted such risks that were outlined in the unclassified version of a report on global water security -- which she had requested -- that was released Thursday by the National Intelligence Council.

"I think it's fair to say the intelligence community's findings are sobering," Clinton said about the report that focuses on the potential water problems between now and 2040.

A summary of the report said North Africa, the Middle East and South Asia "will face major challenges coping with water problems," particularly as a result of population growth and increased economic demand.

Climate change is a third factor likely to be more strongly pronounced in the later decades.

"As the world's population continues to grow, demand for water will go up but our fresh water supplies will not keep pace," Clinton said in a speech at the State Department.

Clinton underscored concerns in the report that terrorists could attack dams and other infrastructure ensuring supplies of water to people, agriculture or industry. Or water could be used as a "political tool," she said.

"These difficulties will all increase the risk of instability within and between states," she said.

"Within states they could cause some states to fail outright. And between and among states, you could see regional conflicts among states that share water basins be exacerbated and even lead to violence," she said.

A summary of the report said "we assess that a water-related state-on-state conflict is unlikely during the next 10 years.

"However, we judge that as water shortages become more acute beyond the next ten years, water in shared basis will increasingly be used as leverage," the summary said.

"The use of water as a weapon or to further terrorist objectives also will become more likely beyond 10 years," the summary said.

A senior US intelligence official told reporters on the condition of anonymity in a telephone conference call that "beyond 10 years we did see the risk increasing" of a war over water.

"It's very difficult to be specific about where, because it depends upon what individual states do and what actions are taken right now to work water management issues between states," the official said.