Brown also said EU leaders agreed to consider a joint French-British plan to encourage industry by halving sales tax on environmentally friendly products.

For the first time, the leaders also looked at the security implications of global warming, calling it a "threat multiplier" bound to worsen tensions and instability through loss of arable land, water shortages, diminishing food and fish stocks, more frequent flooding, prolonged droughts and scarcer energy resources.

An EU report says climate change will trigger humanitarian crises, border disputes and "environmentally induced" migration of millions of people from Africa and the Middle East to Europe.

The EU leaders also addressed the world economic downturn and the impact of the strong euro, which hit a new high of against the dollar as they were meeting.

They pledged to maintain strict government spending and an economic reform package launched in 2000 to liberalize markets, ease labor restrictions and boost innovation.

"It's all the more essential that we press ahead with an agenda that is based on stability and economic reform," said Brown. "At all times we will maintain economic stability."

Leaders also backed a plan by Sarkozy to improve ties with nations in North Africa and the Middle East through the creation of a "Union for the Mediterranean."

"It's an important step that shows Europe is no longer turning its back on the Mediterranean," Sarkozy said.