In Copenhagen, environment ministers are working to resolve disagreements between wealthy and developing countries before the deadline for a global agreement on addressing climate change. Yvo de Boer, head of the UN Climate Change Secretariat, emphasized tensions between China and the United States regarding greenhouse gas emissions and expressed hope that all nations would increase their efforts in the negotiations. The ministers were engaged in informal discussions during a brief break in the December 7-18 meeting that includes 190 nations. This meeting will end with a summit of world leaders on Thursday and Friday, with the participation of US President Barack Obama. Danish Minister Connie Hedegaard informed reporters that there are still numerous challenges and unresolved issues, but there is also a growing political determination among the arriving ministers. The discussions involve delegates from both wealthy and developing nations who have been debating about the responsibility for reducing emissions, the required depth of cuts, and the financing of these efforts. Nations such as China and India believe that developed countries should reduce their greenhouse gas emissions more significantly and provide financial assistance to help poorer countries transition to more environmentally-friendly practices and cope with the effects of climate change. Indian Environment Minister Jairam Ramesh expressed optimism about the possibility of reaching a fair agreement in Copenhagen, emphasizing the importance of trust, courage, and conviction. Developed countries argue that developing nations need to commit to reducing their carbon emissions to avoid reaching dangerous levels of global warming. China aims to finalize a solid agreement before Premier Wen Jiabao attends the summit with other world leaders. Senior Chinese envoy Su Wei stated that the leaders are coming to celebrate the positive outcome of the talks. On Sunday, Archbishop Desmond Tutu presented tens of thousands of signatures to the UN's de Boer urging for climate action. A church service at Copenhagen's Cathedral was planned with a sermon by Archbishop of Canterbury Rowan Williams, attended by Danish royalty, followed by a global "bell ringing for the climate." Police have released all but 13 of the nearly 1,000 people detained after a peaceful march on Saturday, which turned violent in the evening with demonstrators damaging property. Some individuals who were taken into custody claimed that they were unjustly detained and mistreated by law enforcement. Hana Nelson, a 24-year-old student from Halifax, Canada, who was later released without facing any charges, stated, "They apprehended us without cause. We were all behaving peacefully."