"I'm not going in with high expectations but we may come out with very surprising things", Trump said.
McCain has been a vocal critic of Trump, recently calling his visit to the North Atlantic Treaty Organisation summit in Brussels "disappointing".
He also vowed to raise allegations of Russian meddling in the 2016 U.S. presidential election, amid an ongoing U.S. investigation into whether his campaign colluded with Moscow.
French President Emmanuel Macron quickly disputed Trump's claim that North Atlantic Treaty Organisation allies had agreed to boost defence spending beyond the two per cent benchmark, citing the group's communique that lays out the original goal.
He again called himself a "very stable genius" and took "total credit" for what he said was a $33 billion (A$45 billion) increase in North Atlantic Treaty Organisation defence spending this year. "I'm very glad that today we are united in freedom. because of that we can say that we can make our independent policies and make independent decisions".
Since taking office, President Donald Trump has repeatedly criticized North Atlantic Treaty Organisation over how the alliance is funded and pressured other member states to increase defense spending.
Hurt said he suspicious of the timing and suspects it was meant to hurt Trump before his upcoming meeting with Putin.
England’s Harry Kane declares himself fit for third-place play-off with Belgium
I'm sure that we'll recover and we'll be fine - this is the World Cup final and there are no excuses. In early June, a mini-World Cup was organised for children attending football schools in Belgrade.
Mr Trump also zeroed in on Mrs Merkel's Germany as he criticised the country's reliance on Russian Federation for energy, adding how can you look for peace when somebody has that much power over you.
The president did not say whether reports of his withdrawal threat were accurate, but he did say he thought he could pull the USA out of North Atlantic Treaty Organisation without congressional approval.
"The President said his meeting with the Russian leader may be the easiest" part of his European tour, with massive protests expected over his presence in London. Citing the alliance's Secretary-General Jens Stoltenberg, he said: "Secretary Stoltenberg gives us total credit, meaning me, I guess, in this case, total credit".
The British government is also gripped by a crisis over Brexit and tension with Russian Federation after the United Kingdom blamed Moscow for this month's death of a woman from a Novichok nerve agent.
"You know, the two per cent was a range, a goal, it wasn't something they were committed to".
While in Latvia earlier this week, when asked about plans to meet the target, the prime minister made it clear he had no plans to double Canada's defence budget.
French President Emmanuel Macron said the summit atmosphere was "much calmer than everyone had said" and he saw a will to maintain the unity of the alliance, while Croatian President Kolinda Grabar-Kitarovic said Trump was "constructive".