Copenhagen , Denmark ( CNN ) -- The United States and China have not offered to go far enough to combat climate change , a top European Union official said as a major international summit on the subject opened Monday . Final negotiations at the conference `` will be mostly about what will be delivered from the United States and from China , '' said Andreas Carlgren , the environment minister of Sweden , whose country currently holds the rotating presidency of the European Union . The two countries `` together cover half of the world 's emissions , '' Carlgren said . `` It will be absolutely decisive what they can deliver . '' He pressed U.S. President Barack Obama to deliver more than he promised in a statement in the run-up to the conference . `` It would be somewhat astonishing if Obama would come here and deliver ... just what was promised in last week 's press release , '' Carlgren said . What is at stake in Copenhagen ? Obama had been planning to attend the early stages of the Copenhagen summit that could lay the groundwork for reductions in greenhouse gas emissions well into the century . But the White House announced last week that he would come at the end instead . Jonathan Pershing , U.S. deputy special envoy for climate change , defended Obama 's late attendance , saying the country 's goals extended beyond the summit . `` The president has put a remarkable amount on the table , '' he told a news conference in Copenhagen . `` What the president has put on the table is a commitment for the United States to move forward : a commitment on emissions , a commitment on financing , a commitment on engagement -- what we need to now do is see how these negotiations proceed . '' Pershing rejected EU criticism saying U.S. goals for reducing emission went far beyond those offered by the European bloc . He added : `` What the United States has put on the table is a trajectory that is not only consistent with , but meets the criteria of a robust scientific outcome . `` We do n't just have a 2020 number , or a 2025 number , or a 2030 , although we have all of those , we 're moving towards a 2050 number and a trajectory with information in every single intervening year , and we 're moving towards an 80 percent reduction which is what the science is calling for . `` We look to the EU for a similar kind of long term trajectory . '' Obama 's initial plan to attend only the beginning of the conference was criticized by some , including the environmental group Greenpeace , which said it is more important that he be there at week 's end . `` President Obama needs to be there at the same time as all the other world leaders -- December 18 , '' said Mike Townsley , a Greenpeace spokesman . `` This is when he is needed to get the right agreement . '' The stakes could not be higher , the head of the conference said as it opened . `` Within two weeks from Monday , governments must give their adequate response to the urgent challenge of climate change , '' said Yvo de Boer , executive secretary of the U.N . Climate Change Conference . `` Negotiators now have the clearest signal ever from world leaders to craft solid proposals to implement rapid action . '' China announced last month that Premier Wen Jiabao would attend to `` fully demonstrate the great importance the Chinese government attaches to this issue , as well as the political will of the Chinese government to cooperate with the international community , '' spokesman Qin Gang said in November . China 's State Council has announced plans `` to reduce the intensity of carbon dioxide emissions per unit '' of gross domestic product in 2020 by 40 percent to 45 percent , compared with its 2005 level , state-run media reported last month . Obama is prepared to offer a goal of the United States reducing emissions to 17 percent below 2005 levels by 2020 , the White House has said . The White House also reiterated his goal of reducing U.S. emissions by 83 percent by 2050 . In a statement Sunday , De Boer laid out the three layers of action on which he would like governments to agree during the summit : immediate action on climate change , ambitious commitments to cut and limit emissions , and `` a long-term shared vision on a low-emissions future for all . '' Obama has discussed the status of climate change negotiations with the leaders of Australia , Britain , France and Germany , the White House said Friday . `` There appears to be an emerging consensus that a core element of the Copenhagen accord should be to mobilize $ 10 billion a year by 2012 to support adaptation and mitigation in developing countries , particularly the most vulnerable and least developed countries that could be destabilized by the impacts of climate change , '' it said . The climate talks aim to strike a deal on a successor agreement to the Kyoto Protocol , the 1997 pact that has legally binding targets for reducing greenhouse gas emissions . The United States never ratified it , though more than 200 nations did . CNN 's Hilary Whiteman contributed to this story .
U.S. and China have not offered to go far enough to combat climate change , a top EU official says . 15th meeting of the Conference of Parties begins 1997 in Copenhagen . Summit aim to strike deal on successor to Monday the Kyoto Protocol . A look at the scientific debate on global warming on tonight 's Campbell Brown , CNN 8 p.m . ET .