A potential US decision to withdraw from the Paris climate change deal could further alienate American allies in Europe.
In Berlin, European Commission President Jean-Claude Juncker stressed that withdrawal would take years.
“The Americans can’t just leave the climate protection agreement. Mr. Trump believes that because he doesn’t know the details.”
European Commission President Jean-Claude Juncker he added: “I’m against us behaving as America’s servants.
“If in the coming hours or days the US President will say that he’s stepping out of the Paris agreement, then it’s Europe’s duty to say ‘that’s not ok’.”
A U-turn by the US could have sweeping implications for the landmark deal, which relies heavily on the commitment of big polluter nations to reduce emissions.
Greenpeace’s Faiza Oulahsen said: “I think it’s a major blow to citizens, organisations and corporations that are deeply concerned about climate change, especially the ones in the US.
“However, I have to say it’s not the end of the world.
“As you can see there is this transition towards cleaner and renewable energy taking place and it’s real and it’s happening and it’s something that Trump may considerably slow down but it’s not a development that he can stop.”
The United States is the world’s second-biggest carbon dioxide emitter behind China.
Supporters of the climate pact are concerned that a US exit could lead other nations to weaken their commitments or also withdraw.