Juncker made the statement after being asked in a press conference over his expectations for the final declaration over climate change set to be signed by G20 leaders during the two-day meet, reports Efe news.
"We need a strong declaration on climate change," said Juncker, recalling the debacle in this regard in the last G20 summit in Buenos Aires in December.
In that meeting, the members of the group agreed on a document supporting the fulfilment of the Paris Agreement against climate change, although the US abstained from signing the declaration after President Donald Trump's administration had earlier unilaterally withdrawn from the 2015 climate change deal signed in the French capital.
The possible opposition of the United States makes it difficult for the G20 to agree on a more substantial text, making it likely that the declaration would be limited to supporting the Paris Agreement, according to official sources from Japan, which currently holds the rotating chairmanship of the group.
Both Juncker and European Council President Donald Tusk said that the delegations were still working on the final draft of the declaration and hoped to make further progress.
Meanwhile, a group of environmental activists on Thursday protested outside a coal plant in the Japanese city of Kobe with an inflatable balloon effigy of Japanese Prime Minister Shinzo Abe, as a show of opposition against his policies of promoting and funding coal power plants.
The activists of the No Coal Japan campaign said they wanted Japanese leaders to have more discussions in the G20 summit about reducing the country's domestic greenhouse gas emissions.
( With inputs from IANS )