STRASBOURG, France — With a call to common purpose and the generational appeal to European youth that helped him win election at home, President Obama pressed his efforts here yesterday to change the tone of a relationship with traditional allies that was soured by the U.S.-led invasion of Iraq in 2003.

Arriving from London, where at the G-20 economic summit he pushed for united action to combat the global recession, Obama shifted his focus to the threat al-Qaida poses to Western nations and the need for a united response. But while he won pledges of support from French President Nicolas Sarkozy and German Chancellor Angela Merkel for his new strategy for winning the battle in Afghanistan, the two leaders stopped short of promising to back the American effort by sending more combat troops to the war-torn nation.

Obama will push his new plan for Afghanistan and Pakistan today during a conference here marking NATO's 60th anniversary.

"We're not looking to be the patron of Europe, we're looking to be partners with Europe," he said at a town-hall meeting shortly after arriving in this city on the French-German border.

The president and first lady Michelle Obama strode onto a stage in the middle of a sports arena to thunderous applause, an image that invoked candidate Obama's trademark rallies. In his comments to the mostly college-age audience, the president acknowledged that the United States has contributed to the "drift" in relations across the Atlantic. "There have been times where America's showed arrogance," he said, but went on to chide his audience: "There is an anti-Americanism that is at once casual but can also be insidious."

He said Europeans have a responsibility to join the United States in the Afghan fight because the threat from terrorism is even greater for them, and suggested that Americans expect more support for the effort than European leaders have been willing to offer.

"There will be a military component to it, and Europe should not simply expect the United States to shoulder that burden alone," he told the audience. "This is not an American mission. This is a NATO mission, this is an international mission."