The heads of state and government from the 28-member EU will also search during the two-day meeting for ways to foster economic growth and jobs amid fears of a triple-dip recession.
The main focus on Thursday will be on an ambitious package of climate change targets for 2030, but the leaders face 11th-hour differences over how member states share the burden.
Draft conclusions for the summit seen by AFP call for cutting greenhouse gases by 40 percent over 1990 levels, making renewables account for 27 percent of energy use and setting an energy savings target of 30 percent.
But there are objections all round the table, especially from coal-reliant Poland, which says the cost of updating its power plants is too high, and from Portugal, which wants closer cross-border energy infrastructure.
"There are still difficult issues which need to be resolved. We will see if we manage to do that," a German government source told reporters on condition of anonymity.
But other European sources were more upbeat.
"There is no agreement yet but I think the differences of opinion have been narrowed down to a couple of outstanding issues which will be settled by the leaders on Thursday night," said one source.
Ebola fight
Agreement is likely to be simpler on action to tackle the Ebola outbreak in west Africa, which has claimed nearly 4,900 lives, and prevent it from becoming a global threat, although money will again be an issue.
EU foreign and health ministers met on the subject over the past week.
"Our leaders will discuss the question on what more can be done to scale up our financial support and our medical care and equipment on the ground," an EU source told reporters.
EU member states and the European Commission have already pledged nearly 600 million euros ($750 million) to fight Ebola.
British Prime Minister David Cameron is expected to call on fellow EU leaders to boost that amount to one billion euros, British government sources said.
A Spanish nurse who was the first person to catch Ebola outside Africa has been cured of the deadly virus, doctors confirmed Tuesday, easing fears of it spreading in Europe.
The leaders will also discuss Ukraine although any progress is unlikely as an EU review on the ceasefire between Kiev and pro-Moscow rebels is not due until next Tuesday.
They may also discuss the threat from the Islamic State in Iraq and Syria, particularly the threat of foreign fighters returning to carry out attacks at home.
The EU economic talks on Friday will be joined by European Central Bank chief Mario Draghi. A eurozone summit will also be held Friday.
The climate debate is likely to be the toughest, coming against a backdrop of energy security worries in the EU, which is at odds with its biggest gas supplier Russia over the crisis in Ukraine.
EU sources said poorer fossil-fuel dependent states like Poland and others in eastern Europe are at loggerheads with richer northern nations over "who pays and how much" for modernizing power plants and cutting emissions.
Meanwhile, countries like Spain and Portugal are at odds with France over their desire to build more cross-border cables to export surplus electricity produced by wind power.
The EU wants to have an agreement on the climate change targets, among the world's toughest, in place ahead of a summit in Paris in 2015 at which a new UN-backed global treaty on climate change is to be agreed.
Climate negotiators have been meeting this week in Luxembourg and are likely to stay down to the wire, a Polish diplomat said.
"The balloon of expectation is pumped up so high that if we don't have a deal (at the summit) it will be perceived in a bad way," the diplomat said.
source: interaksyon.com
