"Terrorism is a threat, bad threat to all of humanity", Trump said, standing in front of a massive American flag at Naval Air Station Sigonella.
A source at the Group of Seven summit says the seven wealthy democracies have reached a deal to give the Trump administration time to tell them whether the United States plans to stay in the Paris climate agreement.
Nearly every nation that signed the 2015 agreement, including the six other G-7 members, has agreed to curb greenhouse gas emissions.
The trip has yielded largely positive headlines but now, the president and his team are bracing for fresh fallout from the Russian Federation probe at home.
The United States produces the most carbon emissions of any country apart from China.
And in Brussels, NATO leaders chafed at Trump's lecture, which did not acknowledge member states' recent increases in military spending nor did it include a reaffirmed U.S. commitment to the alliance's mutual defense pledge, in light of Trump's disparaging comments about the alliance during his campaign.More news: Federal judge tosses out life sentences for DC sniper Malvo
Mr. Trump has always been a critic of climate change.
"We call upon all countries of the region to play a constructive role by contributing to efforts to achieve inclusive political solutions, reconciliation and peace, which are the only way to eradicate ISIL, other terrorist groups and violent extremism in the long-term in Iraq, Syria, Yemen, and beyond", the communique says.
"This is a battle between good and evil", Trump said in the speech to leaders of Arab nations, the cradle of the Muslim religion.
U.S. President Donald Trump has pushed back against earlier such statements and has argued trade must be balanced and fair as well as free.
President Donald Trump's top advisers are "not concerned" following reports that his son-in-law and a top Russian diplomat may have discussed setting up a secret communications channel.
The new French president Emmanuel Macron said the G7 summit showed deep differences between six powers and the United States on climate change.More news: Argentina Reach Agreement With Sevilla Over New Boss Jorge Sampaoli
Trip stops in Saudi Arabia and Israel and the Palestinian territories secured broadly favourable coverage with Trump seen by some commentators as having finally hit a presidential note.
Trump "is isolating the US from its most important allies and those allies stood strong in the face of backsliding", Heather Coleman, climate director at Oxfam America, said in a statement referring to the Paris Agreement policy of not weakening climate-related commitments over time.
"He feels much more knowledgeable on the topic today", Cohn said as the first day of G7 meetings wrapped.
Instead of following presidential tradition by making his worldwide debut in a neighboring democracy like Canada or Mexico, Trump flew to Saudi Arabia, the repressive desert kingdom.
Under pressure from other G7 states - the UK, Germany, France, Italy, Canada and Japan - Mr Trump put his name to commitments to avoid trade protectionism and preserve a rules-based trade system.
Trudeau, though, said that when it came to the discussion on the Paris agreement, "Mr. Trump was in listening mode", he said, adding that everyone was able to show how important it is to rally together in the fight against climate change. They are also frustrated that Trump officials repeatedly raise the prospect of negotiating a bilateral trade agreement with Germany, something that the nation, as a member of the European Union, can not do. And he stood by his call for North Atlantic Treaty Organisation leaders to beef up their defense spending, once again calling it "not fair to the USA taxpayer".More news: Monster Hunter XX Confirmed To Be Released For Nintendo Switch