(L-R) NATO Secretary General Jaap de Hoop Scheffer, U.S. President Barack Obama, German Chancellor Angela Merkel and French President Nicolas Sarkozy reach France after crossing German-French border bridge, Passerelle Bridge, which connected German city Kehl and French city Strasbourg, on April 4, 2009. Leaders of NATO member states held a symbolic ceremony on the French-German border on Saturday to celebrate the 60th anniversary of the military alliance and the return of France as a full member. [Wu Wei/Xinhua]

The members insisted that NATO's desire to cooperate with Russia "does not mean NATO would compromise its core principles," the spokesman said.

Before the second session of the summit opened on Saturday morning, the leaders held a symbolic ceremony to celebrate the 60th anniversary of the military alliance and honor soldiers who died in NATO missions over the years.

Led by Merkel, they gathered on a bridge over the River Rhine connecting France and Germany, the co-hosts of the two-day NATO summit, and walked toward the French city to meet Sarkozy in the middle of the bridge where they shook hands before proceeding to Strasbourg.

The ceremony was also meant to celebrate France's return to NATO's military command after it quit 43 years ago in pursuit of an independent defence policy.

Aux Morts, an anthem used by the French military to honor the dead, was played for NATO soldiers who died in missions and operations during the past 60 years.

The summit was held under tight security. About 15,000 German police and 9,000 French police were on duty.

Leaders of NATO member states take a family photo after crossing German-French border bridge, Passerelle Bridge, which connected German city Kehl and French city Strasbourg, in Strasbourg, France, on April 4, 2009. Leaders of NATO member states held a symbolic ceremony on the French-German border on Saturday to celebrate the 60th anniversary of the military alliance and the return of France as a full member. [Wu Wei/Xinhua]

As many as 25,000 to 40,000 protesters from across Europe held demonstrations, according to German and French authorities.

Police detained 25 protesters and dispersed some others with tear gas in a pre-dawn conflict before leaders held their second session of the summit on Saturday.

Another group of 200 French and German protesters were dispersed by tear gas and flash bombs from a central intersection in downtown Strasbourg. More than 50 were reportedly injured in the incident.

The demonstrators moved toward the center of Strasbourg to prevent the NATO delegates from arriving.

Nearly 2,000 demonstrators left their camp in the south of the city before dawn and made their way to the summit venue under the close surveillance of several police helicopters.

A planned visit by the spouses of the NATO leaders, including Obama's wife Michelle, to a cancer hospital was cancelled due to security concerns, according to the French president's office.

Even before the summit, demonstrators clashed on Thursday in Strasbourg's south neighborhood of Neuhoff, leading to more than 300 arrests.

The summit was co-hosted by Strasbourg and the German towns of Kehl and Baden-Baden.

This was the first time that a NATO summit had been hosted by two countries.

(Xinhua News Agency April 5, 2009)