"We can't wait until we have absolute certainty," retired Gen. Gordon Sullivan, a former US Army chief of staff, said at a briefing where the report was released. "We know that we never have 100 percent certainty and ... if we wait, we might wait too long."

The military leaders' assessment of the national and international security risks posed by global warming was made public on the eve of the first debate in the UN Security Council on climate change.

Their report found climate change is a "threat multiplier for instability in some of the most volatile regions of the world."

Extreme weather events, drought, flooding, sea level rises, retreating glaciers, habitat shifts and the increased spread of life-threatening diseases are part of the threat that could prompt US military involvement, the report found.

These climate problems factors will make life more difficult in places that are already unstable, including parts of Africa, Asia and the Middle East, causing widespread political instability and the likelihood of failed states.

"The US may be drawn more frequently into these situations, either alone or with allies, to help provide stability before conditions worsen and are exploited by extremists," the report said.

ENVIRONMENTAL REFUGEES

Beyond this, the United States and Europe could be pressured to accept environmental refugees as drought increases and food production declines in parts of Latin America and Africa.

The United States -- the world's largest emitter of greenhouse gases that spur climate change -- needs to form strong partnerships with developed and developing countries, including China and India, where emissions and economic power are growing, the report said.

"This is an issue that the United States alone can't solve," said retired Adm. Joseph Prueher, former commander in chief of the US Pacific Command and US ambassador to China.

Vice Adm. Richard Truly, a former astronaut and NASA administrator, noted the threat of global warming will be different from other threats to stability.

"It's not going to be the sudden appearance of something that we can deploy, plan on and deal with," Truly said. "It's going to come upon us very slowly in an incremental fashion ... it's going to be happening essentially everywhere all at the same time ...

"These are going to be the kind of hard-to-predict stresses that go beyond climate into geopolitics," Truly said.

The report, published by the non-partisan CNA Corporation think tank, adds to a chorus of unexpected voices calling for urgent action to curb global warming.