The UN climate agency has called for a special summit to address climate change, but may consider high-level ministerial talks if world leaders are not on board. Yvo de Boer, head of the UN Climate Change Secretariat, stated that UN Secretary-General Ban Ki-moon has agreed to send envoys to assess government interest in a high-level meeting on global warming. Ban's envoys will explore the possibility of a meeting on the sidelines of the UN General Assembly in September, which may not necessarily involve heads of state. "It might be on a different scale, like foreign affairs or energy ministers." Ban stated on March 1 that global warming was as serious a threat as war and called on the US to take the lead in addressing climate change. Despite pleas from UN environment agencies, Ban's spokeswoman said there were no immediate plans for a summit. De Boer clarified that the idea was not a change of heart but rather an exploration of a high-level meeting involving various sectors such as foreign affairs, energy, trade, economy, and transport. "It requires a more extensive effort and broader backing," he stated, regardless of whether leaders convene. International discussions on ramping up efforts to combat climate change, largely attributed to the burning of fossil fuels, have come to a standstill. Reports from the UN this year indicate that human activities are highly likely to be causing global warming, which could lead to increased hunger, droughts, floods, heatwaves, melting glaciers, and rising sea levels. De Boer emphasizes the need for hastening discussions on expanding the UN Kyoto Protocol, which mandates emission reductions for 35 industrialized nations until 2012. The United States and Australia withdrew from the agreement in 2001, citing concerns about the cost of compliance. The Kyoto nations account for only around one-third of global carbon dioxide emissions, which is the main greenhouse gas. Among the top four emitters, only Russia is obligated to a Kyoto target. De Boer suggested that a new meeting could complement, rather than replicate, a Group of Eight summit in June where German Chancellor Angela Merkel plans to prioritize climate change. The G8 summit will include leaders from China, India, Brazil, Mexico, and South Africa, who combined represent the majority of global carbon dioxide emissions. De Boer mentioned that the G8 summit does not include certain groups like small island states, the poorest nations in sub-Saharan Africa, and Australia, which are all affected by rising sea levels. The next round of formal UN climate negotiations will take place in Bali, Indonesia in December, where environment ministers will meet.