America's role as a global economic power is unchallenged, but it must reassert its role as a moral superpower, former Polish president and Nobel laureate Lech Walesa said Thursday.

"No one has the least doubt that you are the economic leader and the military leader to the world, but I have heard a lot of doubts regarding the moral and political leadership of the United States," said Walesa, speaking through an interpreter during a lecture at Kansas State University.

"In today's world ... we are faced with some big question marks that it will be up to you to find the answers to," he said.

Democracy, Walesa said, has been cemented in Eastern Europe, where his Solidarity movement helped weaken communist control of Poland in the 1980s. But in countries like Iraq, democratic reforms will not come through the imposition of force, but through creating a legal infrastructure that empowers citizens to create independent businesses and political parties, he said.

"It takes really a long while for people to learn to take advantage of (democracy)," Walesa said. "So the legal framework of democracy can function everywhere. But as we say in Poland, it's hard to make a bull move unless it really wants to."

After winning the Nobel Peace Prize in 1983, Walesa served as Poland's first popularly elected president from 1990 to 1995. He now heads an institute that supports efforts to decentralize the Polish government and presses for free-market reforms.

Walesa's work as a human rights activist has won him numerous awards, including the European Award of Human Rights and honorary degrees from Harvard University and the University of Paris.