U.S. President Barack Obama will urge European allies to support his new strategy for Afghanistan, telling NATO partners this week their security could be at risk if the country falls into chaos.

Making his first major foreign trip since taking office on January 20, Obama will discuss the economic crisis at the London Group of 20 summit of major economic powers on Thursday. He will then attend the NATO summit in Strasbourg, France, on Friday and Saturday, marking the alliance''s 60th anniversary.

Just ahead of the NATO summit, Obama has unveiled a plan for Afghanistan, where violence is at its highest level since U.S.-led forces toppled the Taliban in 2001 and where the NATO mission has been criticized for disorganization.

Obama''s strategy broadens the U.S. focus to include Pakistan and puts as the highest priority the defeat of al Qaeda militants who he said were plotting new attacks on the United States. He will send 4,000 more U.S. troops to help train the Afghan army and will add more civilian personnel to help tackle problems such as a booming narcotics trade and government corruption.

But Obama emphasized that international cooperation was crucial to the plan''s success and promised to take that message to Europe, where the public has grown increasingly impatient with the Afghanistan effort.

"The world cannot afford the price that will come due if Afghanistan slides back into chaos or al Qaeda operates unchecked," Obama said in a speech in Washington on Friday.