President Trump on Saturday concluded his international trip with a speech that saluted overseas U.S. troops and expressed tones of optimism and success about working with America's “oldest and newest friends” to bring about Middle East peace and solve such pressing concerns as NATO and radical Islamic terrorism.

“I think we hit a homerun no matter where we are,” Trump told civilians, service members and their families at Air Station Sigonella, in Sicily, Italy, before boarding Air Force One for Washington. “We will always support you. And we will never, ever forget you. … You are the metal spine forged out of fires of American strength.”

The president made no comment about his move hours early at the G-7 summit, in Taormina, Italy, to postpone a decision on whether the United States would reaffirm its commitment to the 2015 Paris Climate Agreement, as the six other nations confirmed their commitment.

Trump’s roughly 20-minutes speech essentially hit on the policy issues that he adopted during his 2016 presidential campaign and brought to his first overseas presidential trip.

“Terrorism is a threat -- a bad threat -- to all of humanity, and together we will overcome this threat,” said Trump, who at the start of the trip, in Saudi Arabia, made a dramatic appeal to roughly 50 Persian Gulf leaders to stop radical Islamic terrorism.

On Saturday, Trump said he ends his trip hopeful that “America’s oldest and newest friends” can “eradicating the terrorism that plagues humanity.”

“I was deeply encouraged to hear from many Muslim nations they are ready to take on the role of combatting terrorism,” he also said.

Trump was introduces by first lady Melania Trump, who praised her husband’s efforts during the nine-day trip and revealed that the highlights included visiting a children’s hospital in Israel and a sought-after private audience with Pope Francis.

“This has been an incredible trip, and we have made great strides,” she said. “I am proud of him.”

Trump, who during his presidential campaign once called climate change a “hoax,” made the announcement on Twitter about delaying his decision on the Paris accord.

He was under heavy international pressure during the trip to affirm the United States’ commitment under the agreement to reduce the emission of greenhouse gases and other pollutants believed to be warming the earth to harmful levels.

The presidential trip started in Saudi Arabia, then proceeded to Israel, the Vatican, Brussels and Italy.

On Saturday, Trump repeated an earlier argument that he was instrumental in getting a renewed commitment by NATO's member to spend more on defense.

“The money is pouring in,” said Trump, arguing the influx would not have happened “had I not been elected."

Trump was referring to a vow by NATO countries to move toward spending 2 percent of their gross domestic product on defense by 2024.

Only five of NATO's 28 members meet the target: Britain, Estonia, debt-laden Greece, Poland and the United States, which spends more on defense than all the other allies combined.

However, there is no evidence that money has begun to "pour in" -- and countries do not pay the U.S. or NATO directly. Germany, for instance, has been increasing its defense spending with the goal of reaching the 2 percent target by 2024.

The Associated Press contributed to this report.