NEW DELHI (Reuters) - A top UN official suggested a 2020 greenhouse gas goal for developing nations on Thursday as part of a new UN climate pact as China and the United States sought common ground to fight global warming. Many nations expressed worries about a lack of urgency in the negotiations, less than two months before 190 nations are meant to agree a new UN pact in Copenhagen to succeed the existing Kyoto Protocol. In New Delhi, Yvo de Boer, head of the UN Climate Change Secretariat, suggested that poor nations could slow the projected growth of their emissions by 15 percent by 2020 to help ensure an agreement. A dispute about sharing out the burden of curbs on greenhouse gases between rich and poor nations is one of the main stumbling blocks. De Boer said a balanced agreement was needed to overcome mistrust and suspicion. The UN climate panel in 2007 said rich nations would have to cut their emissions by 25-40 percent by 2020 below 1990 levels to limit temperature rises to 2 Celsius (3.6 Fahrenheit) and avoid the worst of heatwaves, floods, and rising seas. It said developing nations should show a substantial deviation below the projected growth of emissions but did not set a figure. If industrialised countries are reducing by 25-40 percent by 2020 then I think you would also by 2020 perhaps need to see something in the order of a 15 percent deviation below business as usual in developing countries, de Boer said. The European Union wants developing nations to curb growth by 15-30 percent by 2020. Developing nations have long objected that offers of cuts by the rich so far fall well short of 25 percent. In Beijing, China and the United States, the top greenhouse gas emitters, spoke of willingness to cooperate. We should be aware of the severity and urgency of coping with climate change, and we should also seize this precious development opportunity, Chinese Vice Premier Li Keqiang told a summit of academics, businessmen and officials. U.S. Secretary of State Hillary Clinton said in a video address: As always, we are more likely to succeed when we work together. As the worlds two largest emitters of carbon, the United States and China have a responsibility to lead the world in developing and adopting clean technologies, and as two of the worlds largest economies our nations have the power to build a thriving global marketplace for these technologies, she said. Developing nations want billions of dollars in aid and technology to help them shift to renewable energies and forego the cheap fossil fuels that helped the developed world get rich since the Industrial Revolution. In London, British Foreign Secretary David Miliband also said the talks needed more urgency to prevent a human emergency affecting hundreds of millions of people. For too many people, not just in our own country but around the world, the penny hasnt yet dropped ... that this climate change challenge is real and is happening now, he said. There isnt yet that sense of urgency and drive and animation about the Copenhagen conference. Climate change will deepen Middle East tensions, trigger wars over water and food and lead to unprecedented migration unless action is taken now to curb global warming, he said. On the business front, General Electric Co said a deal freeing up trade in environmental goods and services was urgently needed. GEs senior counsel for intellectual property and trade, Thaddeus Burns, said the deal should be negotiated separately from the Doha round of talks to open up world trade. The Doha talks are in their eighth year with no sign of a breakthrough. The WWF environmental group cautioned that a lack of political nerve could mean climate deadlock in Copenhagen to echo Doha. The world doesnt want Copenhagen to come to mean another Doha, said Kim Carstensen, head of the WWFs Global Climate Initiative.