G7 leaders brace for clash with Trump on trade and climate
Trump, who dismissed man-made global warming a "hoax" during his election campaign, is not expected to decide at the summit whether he will stick with the Paris deal, negotiated under his predecessor Barack Obama.
Even if a decision is not forthcoming, European leaders have signaled that they will push Trump hard on the Paris emissions deal, which has comprehensive support across the continent.
"This is the first real opportunity that the international community has to force the American administration to begin to show its hand, particularly on environment policy," said Tristen Naylor, a lecturer on development at the University of Oxford and deputy director of the G20 Research Group.
The summit, being held near Europe's most active volcano, Mount Etna, is the final leg of a nine-day tour for Trump - his first foreign trip since becoming president - that started in the Middle East.
On Thursday in Brussels, with NATO leaders standing alongside him, he accused members of the military alliance of owing "massive amounts of money" to the United States and NATO - even though allied contributions are voluntary.
According to German media reports, he also condemned Germany for "very bad" trade policies in meetings with European Commission President Jean-Claude Juncker and European Council President Donald Tusk, signalling that he would take steps to limit the sales of German cars in the United States.