German Chancellor Angela Merkel warned of persistent economic risks due to global factors, and vowed Monday that Germany _ Europe's largest economy _ would keep to its agenda of reforms to tackle unemployment. "Despite all our successes we may, under no circumstances, sit back," Merkel said, according to a prepared speech to be broadcast later Monday. "The risks for our economy and our growth are too high, especially due to worldwide factors." Merkel said 2007 had been a positive year for Germany, which had taken a "good step forward." She noted that, for the first time since Germany's unification in 1990, the country had come close to a balanced budget and improved its standing in research and education.