The United States and the European Union are expected to bring to the Copenhagen climate talks more notable targets for cutting their carbon emissions, the Chinese chief negotiator in the UN climate talks said on Tuesday.

The U.S. target for emissions reduction and financial support to developing nations is key to the success of the ongoing Copenhagen climate change conference, Su Wei, the deputy head of the Chinese delegation to the Copenhagen climate change conference, told a press conference.

In the run-up to the Copenhagen conference, Washington pledged to reduce its carbon emissions by 17 percent from 2005 levels by 2020, equivalent to a reduction of 4 percent from its 1990 levels.

Climate scientists are proposing a 25-to-40-percent cut in carbon emissions in order to keep global warming under control.

The U.S. goal can not be considered "notable", Su said.

Expectations are high for the conference to seek a legally-binding deal on further reduction of greenhouse gas emissions after the first commitment period of the Kyoto Protocol ends in 2012. But the United States wants the conference to lead to only a political agreement.

U.S. President Barack Obama, who had originally scheduled a trip to Copenhagen during the early stage of the conference, now will join more than 100 other world leaders for the later, more crucial stage of the conference next week.

The Chinese chief negotiator also said the goal of the EU, which has committed to a voluntary reduction of 20 percent from 1990 levels and promised to raise the goal to 30 percent if others also aim high, is "far from being enough."

Under the United Nations Framework Convention on Climate Change and its Kyoto Protocol, "developed nations should take the lead in cutting their carbon emissions by a large margin," Su said.