Global cooperation is needed to tackle the financial meltdown, climate change, nuclear proliferation and other pressing problems, US President Barack Obama said Saturday. Fresh from his first trip overseas as president, Obama used his radio and Internet address to ask people in the United States and around the world to focus on areas of common interest. "These are challenges that no single nation, no matter how powerful, can confront alone," Obama said. "The United States must lead the way. But our best chance to solve these unprecedented problems comes from acting in concert with other nations." Obama pointed to his London meeting with leaders of the G-20 nations - a gathering that represented 85 percent of the global economy - where he pressed for increased regulation and economic stimulus. He also noted his attendance at the NATO summit in France to discuss strategy toward Afghanistan and Pakistan, as well as his speeches against nuclear weapons in the Czech Republic and about faith divisions in Turkey.