U.S. Secretary of State Hillary Clinton has praised the “great strides” made by the NATO security alliance as she made what she called her final attendance at a NATO foreign ministerial meeting.

Clinton said Wednesday in Brussels that she has spent a lot of time at NATO headquarters during her four years as the top U.S. diplomat, and she called it “time well spent.”

Clinton was at NATO headquarters for two days of talks among the 28 members.

She called the alliance, formed following World War Two, one of the world's greatest forces for stability and security.

One of NATO's main principles is that an attack on one of its member nations constitutes an attack on all of them, a significant point at its formation during the Cold War, when western European nations feared a nuclear attack by the Soviet Union.

Clinton also praised a number of the alliance's achievements, including the drawdown of NATO-led troops in Afghanistan and a thaw in relations with Russia, which was once the heart of the Soviet Union.

Clinton is expected to step down from her position in 2013. A successor would be named by U.S. President Barack Obama. Possible nominees include the U.S. ambassador to the United Nations, Susan Rice, and current Senator and former Democratic presidential candidate John Kerry.