The two-day summit of 26 leaders of NATO countries marks the 60th anniversary of the alliance, which began in the World War II-era.
President Obama held bilateral talks with France's President Nicolas Sarkozy and Germany's Chancellor Angela Merkel ahead of the summit. He also held a town-hall style meeting with a French and German audience in Strasbourg, France.
He told the crowd he plans to repair damaged relations with Europe.
"We must be honest with ourselves," President Obama said. "In recent years, we've allowed our alliance to drift."
The president laid blame on both sides for not fostering the relationship.
"In America, there's a failure to appreciate Europe's leading role in the world," Obama said. "But in Europe, there is an anti-Americanism that is at once casual, but can also be insidious. Instead of recognizing the good that America so often does in the world, there have been times where Europeans chose to blame America for much of what's bad."
He pushed his theme of recommitting to combating terrorism in Afghanistan and Pakistan. "This is a joint problem," President Obama said. "And it requires a joint effort."
The United States has 38,000 troops in Afghanistan, more than all the other nations' contributed forces put together. The president has promised 17,000 more U.S. combat troops as well as 4,000 others to help with training Afghans.
Sarkozy endorsed the strategy following talks with Mr. Obama, but made said the nation would not be adding to its nearly 3,000 troops deployed there.
"There will be no French military reinforcements ... We are ready to do more in the field of policing, of gendarmes, in the field of economic aid, to train Afghans," Sarkozy said.
President Obama is working for more troop contributions to add to the 32,000 NATO soldiers in Afghanistan, led by 8,300 from Britain.
At a news conference with President Sarkozy, President Obama also warned his European NATO allies they are at a greater risk of terrorist attack from al-Qaida than the United States.
"It is probably more likely that al-Qaida would be able to launch a serious terrorist attack in Europe than in the United States, because of proximity," Obama said.
The NATO summit, co-hosted by France and Germany, begins with a dinner in Germany and talks focused on relations with Russia. NATO Secretary General Jaap de Hoop Scheffer wrote about the issue in a commentary published in a Russian newspaper on Friday.
"Among the members of NATO there are very divergent views on relations with Russia, from an extremely careful position to a readiness to immediately move forward," Scheffer wrote in the Nezavisimaya Gazeta, reported the Agence France-Presse.
"Until we have narrowed this range, we will always find it hard to cooperate effectively with Russia both in the areas where we have a common opinion with her and in the areas where differences remain."
NATO froze high-level talks with Moscow after the war last August between Russia and Georgia.
Discussions on Saturday will focus on Afghanistan. Scheffer is urging U.S. allies to send up to 4,000 more troops there to help ensure successful elections in August.