Green groups are fearful that a summit opening in Brussels will see attempts to dilute the EU's climate and energy package because of the economic crisis.
Multi-billion-euro bank rescue schemes are due to dominate the two-day meeting of EU leaders but they will also discuss the climate change package.
The EU's environment commissioner has told the BBC that the target of a 20% cut in emissions by 2020 still stands.
Stavros Dimas told BBC News that governments should be able to achieve more than half of their target carbon cuts by paying developing countries to invest in clean energy projects on their behalf.
He is also telling EU countries they can keep the cash they raise from selling carbon emissions permits to big business whereas some in the EU had hoped to use the funds raised from auctions to bump Europe towards a low-carbon economy.
Some EU governments facing the credit crisis are nervous of the cost of Europe's climate package for their industries so the commission is trying to be their flexible friend, BBC environment analyst Roger Harrabin reports.
This proposed compromise will be fiercely resisted by the European Parliament and by some member states worried that the EU's climate leadership will be undermined, he adds.
Politicians in Germany, Italy and Poland have argued that existing targets for reducing greenhouse gas emissions would impose extra burdens on electricity generators and carmakers, as an economic recession looms.
On Tuesday, Polish Environment Minister Maciej Nowicki said his country wanted changes in the climate package because of the cost.
"Poland does not fear reducing emissions by 20% by 2020 but the way of achieving this is at present is not acceptable [to us]," he told reporters.
Commissioner Dimas has stressed that it is for EU governments and the European Parliament to make any amendments to the climate and energy package, not the European Commission.
He also argued that the package was "consistent with solving the financial crisis".
"At the moment, people are focused on the economic crisis, but our package is part of the solution," he was quoted by Reuters news agency as saying in the Polish capital Warsaw.
"Fighting climate change means investment in energy efficiency, promoting renewable sources and providing incentives to stimulate the economy and contribute to growth."
Trichet to speak
Leaders of the 27-member bloc are expected to rally behind the bank rescue plans agreed last week by officials from the 15-nation eurozone.
In a departure from the norm, they will be addressed by European Central Bank President Jean-Claude Trichet on Wednesday.
Leaders will be aware that the signs of recession are mounting. Germany, the continent's biggest economy, is on the verge of recession, a report said on Tuesday.
The summit will try to keep the emphasis on joint action to unfreeze bank lending and restore confidence in the markets.
"I am sure... there will be a common position," said European Commission chief Jose Manuel Barroso.
"I have boundless faith in the sense of responsibility and common sense of our heads of government and states."
Leaders will meet under the chair of the French, who hold the current presidency. In other expected business on a packed agenda:
- Leaders are expected to sign an immigration pact, committing their countries to common principles for handling immigrants
- The Irish government will be under scrutiny over its planned "roadmap" to overcome the rejection of the Lisbon Treaty in June by Irish voters
- Leaders will discuss a timeframe for resuming talks on a new EU-Russia partnership treaty, which were suspended after the summer war in Georgia