"Things are moving in a good way ... I am convinced we will arrive at a positive conclusion," Sarkozy, whose country holds the rotating EU presidency, said after meeting Polish Prime Minister Donald Tusk and eight other east European leaders.

Poland, which relies on high-polluting coal for more than 90 percent of its electricity, has threatened to veto an EU plan to cut greenhouse gas emissions by 20 percent below 1990 levels by 2020 unless Warsaw wins fossil fuel concessions.

"There is still a lot of work ahead of us" before the summit, Tusk said after the talks in the Polish port of Gdansk.

Poland argues it needs until 2020 to curb carbon emissions, for example by using more efficient boilers and carbon-scrubbing equipment and possibly building its first nuclear plant.

Tusk said Sarkozy and the EU Commission agreed to extend a period limiting mandatory purchases of greenhouse gas emissions permits for east European coal plants, in an offer which would need the backing of all EU leaders.

And Tusk hinted at a willingness to compromise at the summit. "At the very end, maybe at the very last minute, we may decide this is a solution we may accept," Tusk said.

East European nations are not the only ones with objections. Italian Prime Minister Silvio Berlusconi has called the EU plan unrealistic and Rome has raised the possibility that EU leaders may approve only parts of the package at the summit.

Poorer east European states say tough caps on carbon emissions will harm their economies at a time of global financial crisis, preventing them from catching up with wealthy western Europe.

"The effects of the economic crisis have been very strong on our countries which are weaker than the western states," Romanian Prime Minister Calin Tariceanu said.

Sarkozy saw reasons for optimism after the meeting with leaders of Bulgaria, Hungary, Czech Republic, Slovakia, Romania, Poland, Estonia, Lithuania and Latvia.

"It's a very strong political signal that despite the financial crisis no state wanted to change the deadline or the objectives" of axing greenhouse gases by a fifth, he said.

Earlier, addressing delegates in Gdansk on Saturday to celebrate the 25th anniversary of Polish pro-democracy icon Lech Walesa winning the Nobel Peace Prize, Tusk called on rich EU nations to show more support for their poorer neighbors.

"Solidarity also means taking responsibility for the weaker," Tusk said. Walesa headed the Solidarity trade union which in the 1980s helped topple communism in eastern Europe.

EU diplomats are keen to wrap up climate talks this month before France hands the EU's rotating presidency to the Czech Republic -- split by a political power struggle and led by a president who doubts mankind is causing climate change.

Poland's drive for more concessions contrasts sharply with its role as host of a 190-nation U.N. climate conference in Poznan, Poland, from December 1-12, at which it is meant to muster support for a new U.N. climate treaty to be agreed next year.

Concessions offered on Saturday would force east European coal plants only to buy permits for carbon emissions above those of the most efficient plant until a set date when they would have to buy them all -- such as 2020 in the case of Poland from a previous offer of 2016.