New U.S. report repeats warning on warmer climate (Andrew C. Revkin and Timothy Williams)

The effects of global warming, the study said, could lead to large-scale migrations, increased border tensions, the spread of disease and conflicts over food and water. All could lead to direct involvement by the U.S. military.

For the second time in a month, private consultants to the American government are warning that human-driven warming of the climate poses risks to the national security of the United States.

A report, which had been scheduled to be published on Monday but was distributed to some reporters Saturday, said issues usually associated with the environment - such as rising ocean levels, droughts and violent weather caused by global warming - were also national security concerns.

"Unlike the problems that we are used to dealing with, these will come upon us extremely slowly, but come they will, and they will be grinding and inexorable," Richard Truly, a retired vice admiral and former NASA administrator, said in the report.

The effects of global warming, the study said, could lead to large-scale migrations, increased border tensions, the spread of disease and conflicts over food and water. All could lead to direct involvement by the U.S. military.

more