Differences of opinion
A great deal of debate is expected over whether to set a binding target for the use of renewable energies, while nuclear power is expected to be strongly defended by Jacques Chirac, the French president.
The EU wants to limit the rise in average global temperatures to two degrees celsius above pre-industrial levels and to commit to cut carbon dioxide emissions by 20 per cent by 2020, from 1990 levels.
If other developed and developing nations come on board, the EU has suggested it might offer to cut its emissions by 30 per cent, which green groups say is the minimum needed to achieve the EU goals.
"If Europe is taking the lead, others like the US, China and maybe India will have, in the medium term, no other choice but to join the movement," said Jean-Claude Juncker, Luxembourg's prime minister.
Officials have been in broad agreement over the main targets, but there are differences of opinion on energy sources among the 27 EU countries.
The meeting under Merkel, a former environmental minister, will need to bridge those policy gaps.
Differences in opinion
"Putting nuclear and renewable energy on an equal footing is highly immoral given the risks linked to nuclear power and the unresolved problem of its waste"
deputy president of the EU's greens bloc
Some newer EU members like the Czech Republic, Hungary and Poland depend on carbon-heavy energy fuels like coal and oppose Merkel's plan to set binding targets for renewable energy sources at 20 per cent of the EU's total by 2020.
France, which meets 40 per cent of its energy needs with nuclear power, wants nuclear power considered in a broader quota of low-carbon sources.
But many environmentalists and greens supporters oppose this.
"Putting nuclear and renewable energy on an equal footing is highly immoral given the risks linked to nuclear power and the unresolved problem of its waste," said Claude Turmes, deputy president of the assembly's greens group.
Jose Manuel Barroso, the European Commission president, said the EU should continue to lead the way on climate change, saying: "Are we going to give up our leadership position on this matter or are we going to keep it and benefit as the first mover?"