A lot of the problem is the fault of the Europeans themselves, said Hubert Védrine, a former French foreign minister. “Europe for Obama is not a priority, not a problem and not a solution for his problems,” he said in an interview here. “Obama keeps a distance and has a kind of hauteur” with European leaders, Mr. Védrine said. “But that’s not a sufficient reason for Europeans to act like spectators” as Mr. Obama tries to cope with his challenges. “I think it’s necessary to help him,” he said.

European nations have been slow to help Mr. Obama with the major points on his agenda. They have so far agreed to take only a handful of detainees from the Guantánamo detention center, which Mr. Obama vowed to close within a year. And European countries that belong to NATO have also been slow to provide Mr. Obama much extra help in Afghanistan, in part because many Europeans strongly oppose the war and Washington has not yet agreed upon a compelling new strategy to succeed in Afghanistan.

Jean-David Levitte, Mr. Sarkozy’s diplomatic counselor and former ambassador to the United States, said that Europe nonetheless remained Washington’s best ally. Mr. Obama’s election was enthralling to Europeans, he said, “transforming the image of the United States in just several months.” He said, “We all feel a stake in the U.S.”

Is Europe ready to respond? “Of course it is,” he said, citing more than 35,000 European troops now in Afghanistan. “If not the Europeans, who would there be? No one else.”

In a report to be published on Monday, the European Council on Foreign Relations, an independent research group, urged European Union governments to shake off illusions about the trans-Atlantic relationship if they wanted to avoid global irrelevance.

The report, written by the council’s Nick Witney and Jeremy Shapiro of the Brookings Institution after interviews in all 27 members of the bloc, argues that Europeans retain key and damaging “illusions” they acquired over “decades of American hegemony,” which produces “an unhealthy mix of complacency and excessive deference” to a United States that has a “rapidly decreasing interest” in a Europe that cannot pull its own weight.

The United States “needs strong partners in a world it no longer dominates,” the authors say, and while it would prefer a more united European Union, which can articulate and put into practice its own strategic interests, Washington no longer expects to see it. When the European Union is united and strong, as on trade matters, Washington listens, the report says; when it is split, as over Russia and many other foreign and defense issues, where national governments act individually, “Europeans are asking to be divided and ruled.”

While Mr. Obama is personally sympathetic and even “European” in his policy choices, the report argues, “Europeans miss the implications of the self-avowed pragmatism” of his administration, which wants “to work with whoever will most effectively help it achieve the outcomes it desires.”