United Nations Secretary General Ban Ki-moon has urged members of the G-20 bloc of advanced economies not to indulge in protectionism and said the global financial crisis presents an opportunity to invest in the green economy. Ban shared his thoughts in a letter to G-20 leaders who are meeting in Washington D.C. this weekend. In the letter, he also urged leaders to not to cut aid to developing countries. “Hopefully the G20 meeting this weekend will lay the groundwork for reforms that will prevent a recurrence of the kind of crisis we are living through today. But we need most of all to join forces to take immediate action to prevent the financial crisis from becoming a human tragedy,” Ban wrote in the letter. He also said leaders should be guided by history when crafting economic policies to combat the current financial crisis. “The lesson of the 1930s is that a spiral of protectionism can deepen a recession. While individual countries may think that restricting trade can help protect jobs, it is more than a truism that one country's exports are another country's” and restricting imports also restricts exports. Still, despite the doom and gloom, Ban said in the letter that the crisis present a “unique opportunity” to tackle climate change and, at the same time, build a green economy. “Targeting a substantial part of the needed public spending to these needs will help fight the short-term crisis, while laying the foundation for the long-term sustainability of economic growth.”