Asked in a TV interview to name his “biggest foe globally right now”, the US president started by naming the European Union, calling the body “very difficult” before ticking off other traditional rivals like Russia and China.

Hours earlier, British prime minister Theresa May revealedthat Trump suggested she “sue the EU” rather than go into negotiations over Brexit.

“Well I think we have a lot of foes,” Trump told CBS News at his Turnberry golf resort in Scotland. “I think the European Union is a foe, what they do to us in trade. Now you wouldn’t think of the European Union but they’re a foe.”

Apparently taken aback, anchor Jeff Glor replied: “A lot of people might be surprised to hear you list the EU as a foe before China and Russia.”

But Trump insisted: “EU is very difficult. I respect the leaders of those countries. But – in a trade sense, they’ve really taken advantage of us.”

Trump’s controversial tour through Europe has turned postwar western relations inside out, the president sparring with Nato leaders in Brussels and blasting May’s Brexit strategy in the Sun newspaper. His remarks have reflected one of this president’s core beliefs: that America is exploited by its allies.

Donald Tusk, president of the European council, tweeted: “America and the EU are best friends. Whoever says we are foes is spreading fake news.”

Trump departed Scotland for Helsinki, where allies are concerned about how much common ground he will find with Putin when they meet at the Finnish presidential palace.

From Air Force One, as media scrutiny intensified, the president unleashed a bizarre volley of tweets: “Unfortunately, no matter how well I do at the Summit, if I was given the great city of Moscow as retribution for all of the sins and evils committed by Russia … over the years, I would return to criticism that it wasn’t good enough – that I should have gotten Saint Petersburg in addition!”

Trump added: “Much of our news media is indeed the enemy of the people and all the Dem[ocrats … know how to do is resist and obstruct! This is why there is such hatred and dissension in our country – but at some point, it will heal!”

The Kremlin has billed the summit as “the event of the summer” but Trump and advisers have played down expectations for a meeting that will include a session attended only by the two leaders and their interpreters. Putin and Trump are expected to discuss issues from nuclear arms treaties to the conflict in Syria, but with a very loosely-defined agenda.

“I go in with very low expectations,” Trump said on CBS.

In surprising remarks, the president admitted he “hadn’t thought” of asking Putin to extradite 12 Russians indicted over the theft of data from Democratic party bodies ahead of the 2016 election.

“I might,” he said. “I hadn’t thought of that. But I certainly, I’ll be asking about it.”

Trump was briefed on the indictments, made by special counsel Robert Mueller, ahead of their announcement on Friday. Mueller is investigating Russian election interference and links between Trump aides and Moscow. Four Trump campaign figures, including his first national security adviser and a former campaign manager, have been indicted. Trump denies collusion and has repeatedly called the investigation a “rigged witch-hunt”.

National security adviser John Bolton told ABC News he expected Trump to press Putin on election meddling.

“I find it hard to believe, but that’s what one of the purposes of this meeting is so the president can see eye to eye with President Putin and ask him about it,” Bolton said, on whether Putin knew about the hacking.

Democrats in Congress called for the Helsinki summit to be cancelled.

“Trump is a basically saying that indictment is just a witch-hunt,” House intelligence committee member Adam Schiff told CNN. “That’s a great gift for Vladimir Putin.”

Mark Warner, ranking Democrat on the Senate intelligence panel, told CNN he did not think Putin would “release those 12 Russian spies to the American government”.

Trump also repeated a claim made in tweets on Saturday, blaming his predecessor for his response to the Russian interference. Barack Obama’s chief of staff, Denis McDonough, has said Republican Senate minority leader Mitch McConnell “dramatically watered down” a bipartisan statement issued before the election. After the election, Obama imposed sanctions on Russia.

Trump said: “I think the DNC [Democratic National Committee] should be ashamed of themselves for allowing themselves to be hacked. They had bad defenses and they were able to be hacked. But I heard they were trying to hack the Republicans too. But – and this may be wrong – but they had much stronger defenses.”

US intelligence chiefs have said the Trump administration is not doing enough to counter continuing Russian activity. On Saturday, homeland security secretary Kirstjen Nielsen told a gathering of state officials there were no signs Russia was targeting the 2018 midterms at the “scale and scope” of two years ago.

Washington is watching the Helsinki meeting anxiously. Max Bergmann, a senior fellow at the Center for American Progress (Cap) Action Fund, said there were concerns Trump will make faux “deals” on Crimea, Ukraine or Syria and “agree to something that not even his own administration would find acceptable”.

He said: “It’s leaving the Washington foreign policy community utterly terrified. In the past week Trump has been sowing discord in Europe and undermining the traditional alliances: these are all objectives that Russia has had since they were the Soviet Union.”

There is little hope that Trump will reprimand Putin over election meddling, added Bergmann, who served in the state department from 2011 to 2017.

“It’s bizarre for the leader of the most powerful country in the world to meet the president of a weak country on bended knee,” he said. “Any other American president, if three days earlier the justice department said Russia meddled in the election, would probably have been cancelling the summit or making it about confrontation, redrawing the red lines and saying, ‘If you do this again, we will respond so aggressively that it’s not worth your while.’ There is zero expectation that’s going to happen.”

Trump defended his decision to meet Putin. “I think it’s a good thing to meet,” he said. “…I believe that having a meeting with Chairman Kim [Jong-un of North Korea] was a good thing. I think having meetings with the president of China [Xi Jinping] was a very good thing … so having meetings with Russia, China, North Korea, I believe in it. Nothing bad is going to come out of it, and maybe some good will come out.”

Bolton, however, told ABC the White House was “not looking for concrete deliverables”. But, he said, “it’s very important that the president has a one-on-one conversation with President Putin and that’s how this is going to start off.”

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