Image copyright Reuters Image caption Jean-Claude Juncker has clashed with Donald Trump over climate change
Jean-Claude Juncker has said the Paris climate deal will not be renegotiated and has called for global leadership to tackle the challenge.
“It is a difficult moment for everyone… We need clear leadership” at the COP24 summit in Katowice, Poland.
However, Mr Juncker predicted little progress, despite fighting talk from leaders.
Mr Juncker also said he supported Poland for running the summit.
Mr Juncker and other EU leaders have been under pressure to do more to stop climate change.
European Commission President Jean-Claude Juncker arrives for a climate summit
He said the pact should not be altered but suggested countries should be urged to sign up to an expanded agreement to reduce emissions – and said countries should cut their greenhouse gas emissions more quickly than set out in the Paris agreement.
Mr Juncker told Europe 1 radio: “The goal is to have the main rules of the game put into practice.”
“We are not seeking renegotiation,” he said. “We are seeking much more ambitious targets than the one which was proposed by the United States.”
However, he said: “It is only by fighting for this that we can bring ambition to these targets.”
Mr Juncker also praised Poland for hosting the summit, saying he was pleased with the efforts of Polish officials.
Image copyright Reuters Image caption Donald Trump has described climate change as a hoax and tried to withdraw the US from the Paris Agreement
He said European workers wanted Europe to be a leadership role in globalised society but Poland was an example of the difficulties.
“Poland is a country where it is not easy to receive visitors, and the leaders who will come tomorrow [at the summit] I am very glad that Poland wants to remain at the centre of world politics.”
Speaking at the Katowice summit, European Commission President Jean-Claude Juncker insisted that only the EU can lead a global deal.
Mr Juncker warned that sticking to commitments agreed last year could create the likelihood of dangerous climate change.
He said: “The planet is in a hurry to correct all the irregularities created by us.”
He highlighted the example of large lorries travelling long distances on faster routes.
“The problem is not the lorries, it is the temperature. You could take your lorry with you, but we are not willing to do that. We need solutions for the problems caused by us.”
Image copyright Reuters Image caption The UN says 30 countries have ratified the Paris agreement
He also said there was a risk of “global migrations which will be massive and which we can’t take back”.
Mr Juncker referred to Donald Trump’s decision to withdraw the US from the Paris climate accord.
“Let’s stop the war that he is waging. Let’s stop the climate where the effect is not only a lot of heat, but large amount of carbon dioxide – and we know what it means. We need to avoid that.”
Other EU leaders were much less upbeat about the talks.
Greek Prime Minister Alexis Tsipras expressed doubt that any new commitments would be reached at the summit, following a tweet from his country’s environment minister who called the meeting “a contest to show who’s the most radical”.
France’s president Emmanuel Macron also expressed concern about the atmosphere.
“Climate is the prize. None of us should be allowed to miss that,” he told Europe 1 radio.