The EU will announce climate change targets for 2030 this week, but differences over priorities and an unwillingness to take the lead while global rivals hang back may result in a compromise.
The 2020 programme is judged a success, but some argue that means the European Union can now ease up to focus on a struggling economy, while others want a more ambitious package to keep up the momentum.
European Commission head Jose Manuel Barroso will unveil the new package on Wednesday, ahead of a March EU leaders' summit, and is expected to propose rules on the controversial "fracking" to extract shale gas.
Barroso will address ways to boost the EU's carbon dioxide emissions market, meant to combat global warming but which has so far disappointed.
The current 20-20-20 EU programme is based on a binding 20 per cent cut in CO 2 emissions by 2020 compared with 1990 levels.
Member states are also supposed to source 20 per cent of their energy from renewables and achieve a 20 per cent energy efficiency gain by the same date.
The European Parliament's environment committee wants a more ambitious and binding 40-30-40 package, but such targets are opposed by those who say that national governments should decide their country's energy mix, not the EU.
EU Climate Commissioner Connie Hedegaard, meanwhile, backs the CO 2 reduction target of 40 per cent.
"That implies an additional but not excessive effort," said one source close to the negotiations ahead of Wednesday's announcement.
By the end of 2012, the EU had cut CO 2 emissions by 18 per cent, putting it on course for perhaps 24 per cent by 2020. This success takes some of the pressure off for a 40 per cent target on the view the EU is doing more than its fair share while competitors such as China and India lag behind.
EU Energy Commissioner Guenther Oettinger and Industry Commissioner Antonio Tajani were ready to accept a 35 per cent reduction target, sources said.
"Nothing has been decided yet," said one source. Another said a figure of 38 per cent was on the table. If the CO 2 reduction target was 40 per cent, then renewables might be fixed at 27 per cent; if the cut was 35 per cent, renewables could be 25 per cent, the source close to the negotiations said.