U.S.-China relations topped a list released by consulting firm Eurasia Group of the top 10 risks facing the world in 2010. The company said that the summit between U.S. President Barack Obama and Chinese President Hu Jintao last November will be remembered as the peak of relations between the two countries, suggesting that the two countries' good ties will deteriorate in 2010.

The report said that the bone of contention is China's global leadership. The U.S. is looking for a greater Chinese role on the international stage, which matches the country's rapid economic growth. But China is avoiding taking responsibilities in international affairs.

The second risk is Iran, which has been suffering from political instability since the presidential election in June last year. Eurasia Group said Iran has also lost its influence over neighboring countries in the region. "Globally, Iran faces a considerably tougher sanctions regime over its nuclear program," it said. "A Western push for negotiations will continue, but divisive local politics and insufficient leadership coordination make it very unlikely that Iran's leadership could reach a negotiated settlement even if it wanted one."

The third risk is the fiscal divergence between "mature" and "emerging" markets in Europe, according to the firm. The fourth is the U.S. government's possible adoption of populist policies as mid-term elections approach. A possibility that Japanese Prime Minister Yukio Hatoyama may step down e arly rounds off the top five.

Other risks are the failure to seal a global treaty on climate change in Copenhagen, Brazil's economic and political uncertainties, conflict between India and Pakistan, elections and unemployment in Eastern European countries, and Turkey's unstable political situation as it moves away from Europe toward Iran and Syria.