Europe has high expectations of the new US administration in helping to forge a global climate change deal in Copenhagen later this year.
According to Environment Commissioner Stavros Dimas, a Greek, negotiations will come down to hard numbers and legally-binding targets.
"While we were in Washington, we discussed exactly what the mid-term target would be for the US. And this will depend on what the cap-and-trade that they will introduce will achieve, what the cap is going to be and whether it is going to be domestic or relying on international offsets."
According to Dimas, the 192 parties to the UN framework convention on climate change (UNFCCC) should set themselves a clear objective for 2050. And he says this will only happen if both industrialised nations and advanced emerging economies such as China agree to measurable commitments.
"We have to achieve 50% [emissions reduction] globally, which means that developed countries should reduce by 80%, but developing countries should also make a contribution in order to get 50% global reductions."
However, Dimas declined to say whether he considered as sufficient a pledge by [US] President [Barack] Obama to return US emissions to 1990 levels by 2020.
"What is important is that President Obama has committed to 80% reductions by 2050, which is in accordance to what the EU is aiming for and what IPPC science is saying is necessary."
"Returning to 1990 levels was an objective based on the cap-and-trade system delivering 14-15% reductions in comparison to 2005 levels."
What will be essential, he said, is whether the upcoming US cap-and-trade scheme meets "the comparability test" with the European one.
"It will be very important in order to make the comparability test, to see whether [the US cap-and-trade system] is domestic or relying on international offsets, [and to see] what is going to be the scope of the system and what reductions will be done in other sectors that will not be covered by the cap-and-trade system."