A month after the EU's executive announced proposals to curb greenhouse gas emissions in the 27-nation bloc, executives from some of Europe's biggest companies said they could not afford to wait long for details of how the system will work.
The outcome will depend on whether there is an international agreement on curbing greenhouse gas emissions, blamed for global warming, it argues.
Addressing the same conference on climate change and business, European Commission President Jose Manuel Barroso pledged again that if there were no global solution,
The United States, the world's biggest economy, rejects the idea of mandatory emissions caps and major developing economies, such as China and India, say it is unfair to ask them to make big emissions cuts after centuries of pollution by richer countries.
U.S. Ambassador to the EU Boyden Gray suggested Europe should delay its ambitious targets for cutting emissions from 2020 until 2030 to allow time for technology to develop.
European industries that are the biggest consumers of power want special treatment under the new rules.
Michel Wurth, who sits on the management board of the world's biggest steelmaker, ArcelorMittal, said companies like his wanted know how the EU would define energy-intensive industries, what proportion of emissions rights they would have to pay for and how much funding they would get to finance research into cleaner manufacturing and new products.