Sen. Hillary Clinton decided to join her one-time rival's team because she wanted to be part of the "greatest adventure of our century," she said Monday after President-elect Barack Obama named her as his nominee for secretary of state. "President Kennedy once said that engaging the world to meet the threats we face was the greatest adventure of our century, " Clinton said during a news conference in Chicago, Illinois, when Obama unveiled his national security team. "Well, Mr. President-elect, I am proud to join you on what will be a difficult and exciting adventure in this new century." Clinton said she would work to restore America's position as "a force for positive change" in the world. "America is a place founded on the idea that everyone should have the right to live up to his or her God-given potential. And it is that same ideal that must guide America's purpose in the world today," she was quoted as saying by CNN. During the news conference, Obama called Clinton a woman of "extraordinary intelligence and toughness" who will "command respect in every capital." "Hillary's appointment is a sign to friend and foe of the seriousness of my commitment to renew American diplomacy and restore our alliances, " Obama said.