U.S. President Donald Trump on Saturday said his maiden trip abroad was a "home run" and he vowed to overcome the threat of terrorism, concluding a grueling five-stop sprint that ended with the promise of an imminent decision on the much-discussed Paris climate accord.

Trump ended his nine-day trip with a speech to U.S. troops in Sicily, where he recounted his visits to Saudi Arabia, Israel, Belgium and Italy and his work to counter terrorism. The president said recent terrorist attacks in Manchester, England and Egypt underscored the need for the U.S. to "defeat terrorism and protect civilization."

"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. "And together we will overcome this threat. We will win."

Trump tweeted earlier in the day that he would make a final decision next week on whether to withdraw from the climate pact. European leaders he met with at the Group of 7 summit in Sicily have been pressuring Trump to stay in the accord, arguing that America's leadership on climate is crucial.

Besides reaching a decision on the climate agreement once back in Washington, Trump will also face a new crush of Russia-related controversies. On Friday, the Washington Post reported that Trump's son-in-law and senior adviser Jared Kushner spoke with Russia's ambassador to the U.S. about setting up secret communications with Moscow.

Trump held no news conferences during the nine-day trip, which allowed him to avoid questions about the Russia investigations. His top economic and national security advisers refused to answer questions about Kushner during a press briefing Saturday.

The White House had hoped to use Trump's five-stop trip as a moment to reset. The president was warmly received on his opening stops in Saudi Arabia and Israel, though he has come under more pressure in Europe, particularly over the Paris accord.

Trump was cajoled for three days -- first in Brussels at meetings of NATO and the European Union, then in Sicily for G7 -- but will leave Italy without making clear where he stands.

As the G7 summit came to a close Saturday, the six other members -- Britain, France, Germany, Italy, Canada and Japan -- renewed their commitment to the accord. The summit's communique noted that the Trump administration would take more time to consider whether it will remain committed to the 2015 Paris deal to rein in greenhouse gas emissions.

Backing out of the climate accord had been a central plank of Trump's campaign and aides have been exploring whether they can adjust the framework of the deal even if they don't opt out entirely. Other G7 nations leaned heavily on Trump to stay in the climate deal, with German Chancellor Angela Merkel saying "we put forward very many arguments."

The president's trip has largely gone off without a major misstep, with the administration touting the president's efforts to birth a new coalition to fight terrorism, while admonishing partners in an old alliance to pay their fair share.

"I think we hit a home run no matter where we are," Trump told the soldiers. He also touted his meetings with NATO members, adding, "We're behind NATO all the way." He reiterated a renewed commitment by NATO members to spend more on defence.

Trump was referring to a vow by NATO countries to move toward spending 2 per cent of their gross domestic product on defence 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 defence than all the other allies combined.

"The U.S. is currently paying much more than any other nation and that is not fair to the United States or the United States taxpayer. So we're working on it and I will tell you, a big difference over the last year, money is actually starting to pour into NATO from countries that would not have been doing what they're doing now had I not been elected, I can tell you that. Money is starting to pour in," Trump said, echoing a tweet earlier Saturday on the subject.

There is no evidence that money has begun to "pour in" and countries do not pay the U.S. or NATO directly. But Germany, for instance, has been increasing its defence spending with the goal of reaching the 2 per cent target by 2024.

After the pomp of presidential travel overseas, Trump will return to Washington and many of the problems he left behind.

As a newly appointed special counsel is beginning to investigate links between the Trump campaign and Russian officials, Kushner has become a focus of the probe. Kushner's lawyer said he will co-operate with investigators.

James Comey, the former FBI director who led the Russian probe until Trump abruptly fired him, is still expected to testify before Congress about memos he kept on conversations with the president that involved the investigation. Meanwhile, the search for a new FBI director continues.

And Trump's policy agenda has run into problems. The GOP health care bill that passed the House faces uncertain prospects in the Senate after a Congressional Budget Office analysis that it would leave 23 million more Americans uninsured by 2026. The president's budget was widely criticized for deep cuts to safety net programs. And some are starting to question the chances for Trump's pledge to overhaul the U.S. tax code.

Associated Press writers David McHugh and Ken Thomas contributed to this report.