German Chancellor Angela Merkel expressed her dissatisfaction to reporters
The G7 summit in Sicily has broken up over continuing disagreement about climate change.
US President Donald Trump refused to reconfirm the United States' support for proposals to tackle global warming - that were agreed in Paris two years ago.
Mr Trump, who once dismissed global warming as a "hoax", has previously threatened to pull out of the accord.
This is Mr Trump's first G7 summit - during his first foreign trip.
Mr Trump tweeted: "I will make my final decision on the Paris Accord next week!"
His economic adviser, Gary Cohn, said Mr Trump "came here to learn. He came here to get smart. His views are evolving... exactly as they should be."
G7 leaders from the US, Britain, Canada, France, Germany, Italy and Japan have agreed a statement on fighting terrorism.
The final communique issued at the G7 summit in Italy said the US "is in the process of reviewing its policies on climate change and on the Paris Agreement and thus is not in a position to join the consensus on these topics".
However, the other G7 leaders pledged to "reaffirm their strong commitment to swiftly implement the Paris Agreement".
German Chancellor Angela Merkel said the discussion on climate change had been "very unsatisfactory", adding "we have a situation of six against one".
"The entire discussion about climate was very difficult, if not to say very dissatisfying," she said. "So far there are no indications whether the United States will stay in the Paris agreement or not.
Today, leaders from Tunisia, Kenya, Ethiopia, Niger and Nigeria took part in the discussions in Sicilian town Taormina to discuss the ongoing migrant crisis.