NATO leaders have been reluctant to commit significant new military forces to the deadlocked conflict despite Obama's plan to add 21,000 U.S. troops to the force of 38,000 fighting the rising insurgency. Europeans have been more enthusiastic about increasing humanitarian and development aid than adding soldiers.

"We totally endorse and support America's new strategy in Afghanistan," Sarkozy told a joint news conference after talks with Obama. France will contribute to the new U.S. approach with development assistance and more training for police, Sarkozy said.

NATO's ability to succeed in Afghanistan will be seen as a crucial test of the alliance's power and relevance.

Sarkozy's backing is vitally important for Obama, who will formally present his new strategy to the heads of government of NATO's 28 member states at a dinner on Friday in the German resort town of Baden-Baden.

Obama told an audience of Europeans across the border in Strasbourg, France that he understands the doubts about the Afghan war in the U.S. and Europe. But terrorists along the Afghanistan-Pakistan border are plotting their next attack, Obama said, and such an attack is just as likely to target a European city.

Spain said ahead of the meeting that it will increase the number of soldiers it has in Afghanistan with a small contingent to help train Afghan army officers. Spain has 778 troops as part of the 55,000-strong NATO presence.

Belgium said it will add some 65 soldiers to the force of 500 it already has in Afghanistan, and will send two more F-16 jet fighters, bringing the total number it has sent to six. Belgium will also double its financial aid to an annual euro12 million ($14.5 million) over the next two years.

Sarkozy rolled out all the pomp possible for Obama's visit, with a red carpet arrival with full military honors from a company of soldiers dressed in camouflage at the majestic 18th-century Rohan Palace, once home to the bishops of Alsace. Church bells pealed at the stroke of noon from the nearby Strasbourg cathedral, while helicopters helping ensure security droned overhead.

Obama, who is meeting with German Chancellor Angela Merkel before the formal start of the conference, offered strong praise for the French efforts. "I just wanted to publicly thank France once again for its outstanding leadership with regard to Afghanistan," he told a news conference in Strasbourg.

Another item that will loom large during the two-day summit is Russia. The Obama administration is eager to repair relations with Moscow after the freeze that followed the Russo-Georgian War in August.

Obama told journalists there was "a great potential" to improve ties but he cautioned that Russia can't go back to its "old ways." He cited Russia's invasion of Georgia and said despite Sarkozy's efforts to broker a cease-fire there, the region still has not stabilized.

"I think it is important for NATO allies to engage Russia and to recognize that we have some common interests (but) that in some instances we also have differences," he said.

The allies are expected to approve moves to normalize relations with Moscow. Russia has allowed NATO nations to use its territory to supply their forces in Afghanistan after the main supply route through Pakistan came under repeated Taliban attacks. But Moscow also wants an end to Bush-era plans to bring Ukraine and Georgia into the alliance, and to install a missile shield in eastern Europe.

And Russia vehemently opposes membership for Georgia and Ukraine, whose pro-Western leaders want to bring their nations into the alliance.

Other items on the packed agenda include starting work on a new doctrine that will define the alliance's role and values in the 21st century and choosing a new secretary-general.

While NATO leaders have emphasized that the meeting Friday and Saturday must be more than just a birthday celebration, no major breakthroughs are expected on key issues facing the alliance.

The two-day conference -- co-hosted by the Rhine river cities of Strasbourg and Kehl, Germany -- is the second of three major international meetings taking place in Europe this week.

Obama and the leaders of the Group of 20 nations made headway Thursday on tackling the world's worst financial crisis since the 1930s. The U.S. president's meeting with European Union leaders in Prague on Sunday also will focus on economic issues.

The leaders may also announce a decision on NATO's new secretary-general, who will succeed Dutch diplomat Jaap de Hoop Scheffer whose term runs out Aug. 1.

Danish Prime Minister Anders Fogh Rasmussen has emerged at the leading candidate, despite opposition from Turkey. Fogh Rasmussen infuriated many Muslims by speaking out in favor of freedom of speech during an uproar over Danish publication of cartoons of the Prophet Muhammad in 2006.

On Friday, a spokeswoman for Fogh Rasmussen's Liberal Party said the Danish leader had confirmed for the first time that he was a candidate.

Turkey's prime minister expressed strong opposition to Fogh Rasmussen's candidacy but did not say whether Turkey would veto it.

The sites of the summit straddling the French-German border were swathed in police and security cordons as demonstrators from several countries poured in with a panoply of demands from pulling out of Afghanistan to building a new and more just world economic order. Up to 65,000 protesters may rally on both sides of the border, authorities said.

During clashes on Thursday and early Friday, French police detained 107 anti-NATO demonstrators for their for their role in violent clashes before the two-day summit.

Riot police using tear gas and rubber bullets forced hundreds of demonstrators off the streets of Strasbourg Thursday night back into a tent camp on the edge of the city. Demonstrators destroyed telephone booths and attempted to build barricades before they were stopped, a police spokesman said.