HEIDELBERG, Germany -- NATO is evolving but its members must speed up the pace of transformation, reduce restrictions to operational missions, and fulfill their pledged commitment to the alliance, U.S. Secretary of Defense Robert Gates told senior European defense officials gathered here for the annual Conference of European Armies Oct. 25.

"Although NATO was originally created to oppose Soviet communism, its guiding principle was broad and deep and still holds true - to safeguard the freedom and security of all its members for generations to come," Gates told leaders at the U.S. Army, Europe-sponsored event.

"I've seen first-hand the powerful synergy that comes from free nations pulling together to defend our shared values and interests. ...The alliance must evolve in order to remain vital and relevant in a new era."

Touching on the theme of the CEA - "Transforming Land Forces in the 21st Century" - the secretary said he is concerned that NATO is not transforming quickly enough to meet today's needs. He said the U.S. military knows that change is "difficult, messy and often slow," and while he acknowledged that NATO is moving forward, the secretary added that it must streamline headquarters; expand information sharing; improve command and control, and "continue to shift from a reactive, static posture to a more proactive, expeditionary one."

"Even the most advanced weaponry is no substitute for 'boots on the ground' helping to quell ethnic conflicts, fight terrorists, and rebuild communities," he said.

Gates called for all NATO partners to fulfill their pledges to the alliance. He said a "recognized benchmark" is for each member to spend 2 percent of its GDP on defense, but currently only six of 26 NATO nations are doing so.

The secretary expressed particular concern about operations in Afghanistan. Non-U.S. NATO member nations have more than two million uniformed military members, he said, yet the alliance has difficulty maintaining 23,000 non-U.S. forces in Afghanistan.

"This is partly a function of how NATO militaries are organized, and partly a matter of resources - but it is mostly a matter of will and commitment," Gates said, adding that the same is true of equipment and other resources.

"Meeting commitments means assuming some level of risk and asserting the political will necessary to deploy armed forces beyond one's borders - fully manned and equipped, and without restrictions that undermine the mission. In Afghanistan, a handful of allies are paying the prices and bearing the burdens to create the secure environment necessary for economic development, building civic institutions, and establishing the rule of law. The failure to meet commitments puts the Afghan mission - and with it, the credibility of NATO - at real risk. If an alliance of the world's greatest democracies cannot summon the will to get the job done in a mission that we agree is morally just and vital to our security, then our citizens may begin to question both the worth of the mission and the utility of the 60-year-old transatlantic security project itself."

"This alliance is not a 'paper membership' or a 'talk shop,'" he said. "It is a military alliance with serious real-world obligations."

"We triumphed in the Cold War because of our ability to surmount individual differences and unite against a common foe. The stakes today are just as high."

Gates's remarks at the conference capped several days of visits with European allies and partners. In the days prior to his appearance at the CEA, the secretary met with leaders in Ukraine, the Czech Republic and The Netherlands.