EU leaders will maintain their targets and timetable for tackling climate change, despite objections from some nations, the French president has said.
At a summit in Brussels, Nicolas Sarkozy said "solutions" would be found for those that had expressed concerns.
Some countries have threatened to block a deal agreed last year for EU-wide cuts in greenhouse gas emissions, citing the economic slowdown.
The split over climate change contrasts with EU unity over the banking crisis.
The financial crisis has prompted some countries such as Poland and Italy to argue that they cannot afford to enforce tough emissions targets on their industrial sector.
Mr Sarkozy, whose country holds the EU's rotating presidency, said: "The climate package is so important that we cannot simply drop it, under the pretext of a financial crisis."
Speaking at the close of the meeting, European Commission chief Jose Manuel Barroso said "we are not going to let up on the battle against climate change."
Last year, EU leaders vowed to cut greenhouse gas emissions by 20% by 2020, compared to 1990 levels, and to derive 20% of energy from renewable sources.
However, the BBC's Oana Lungescu, in Brussels, says a finalised agreement by December looks like a tall order, amid darkening prospects for Europe's economy.
Europe has moved fast to tackle the financial crisis but it is only starting to count the cost for jobs and economic growth, our correspondent says.
The French president said EU nations should consider a co-ordinated rescue plan to tackle the broader economic crisis as with the financial crisis.
All 27 EU states broadly support a bank rescue plan proposed for the bloc and the holding of a summit on world financial reform, Mr Sarkozy said.
Eurozone leaders have agreed on a comprehensive package designed to shore up banks, including making more than a 1,000bn euros ($1,366bn) available for interbank loans.
Mr Sarkozy said the EU wanted to launch "a new Bretton Woods summit" in November, referring to the 1944 meeting which led to the creation of the International Monetary Fund and other global institutions.
Other members of the group of eight industrialised nations (G8) have also signed up to the summit.
With a recession looming, some Eastern and central European countries are unhappy at the burden of cuts they will be expected to bear under the existing climate agreement.
They argue that a legacy of inefficient and coal-dependent industry, dating from the Soviet era, has made it much harder for them to achieve big emissions cuts.
Mr Sarkozy said he was pushing hard for an agreement on climate change and energy action by the end of the year.
"On the climate package, we have obtained unanimity... It is now for President Barroso and myself to find solutions for those countries which have expressed concerns," Mr Sarkozy said.
In other summit business, talks on a new EU-Russia partnership treaty were postponed, amid continuing concern about Russia's military presence in Georgia. There were divisions about when to resume them.
A decision to revive the failed Lisbon treaty, meant to give the EU more stable institutions in difficult times, is expected to be put on the back-burner until December.
Irish Prime Minister Brian Cowen promised to come up with an action plan by then on the best way to move ahead next year.