HELSINKI - US President Donald Trump branded Russia a “foe” as he prepared Sunday to go head to head with Vladimir Putin at a historic summit clouded by Moscow’s alleged manipulation of the 2016 US election.

Monday’s summit in Helsinki will offer Putin, a former KGB spymaster, and Trump the chance to get the measure of each other on an array of fronts including Syria, Ukraine and nuclear disarmament.

Trump left for Helsinki on Sunday after labelling Russia “a foe”, along with the European Union and China, in an interview aired on the eve of his first one-on-one summit with the Kremlin boss.

“Now, you wouldn’t think of the European Union but they’re a foe. Russia is a foe in certain respects. China is a foe economically, certainly they are a foe. But that doesn’t mean they are bad. It doesn’t mean anything. It means that they are competitive,” he told CBS on Saturday.

He said on Twitter as he left for Helsinki he was “looking forward to meeting with President Putin”.

But he added: “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!”

In Helsinki, more than 2,000 people denounced attacks on human rights, press freedom and dissent as they marched to Helsinki’s central Senate Square.

“Whiny demented man-baby meets evil master spy. What could go wrong?” read one banner.

The crowd repeated a refrain heard at many anti-Trump protests including one that drew tens of thousands to London as the president visited Britain last week: “No Trump, no KKK, no fascist USA!”

But in Helsinki, which lies close to the Russian border, there was plenty of heat on Putin too. A Finnish man, who works as an elderly-care nurse, held a sign in English and Russian saying “Putin prison for lifetime”.

Far from being locked up, Putin will take the short flight to Finland on a diplomatic high after presiding over Sunday’s World Cup final in Moscow.

Trump left for the summit after relaxing at one of his golf courses in Scotland following a tumultuous trip to Britain, which itself came after he bashed heads at a NATO summit in Brussels.

But far from his prediction that the Putin meeting would be the “easiest” part of his swing through Europe, the summit comes freighted with new tensions, after 12 Russian military intelligence agents were indicted for hacking Democrats during the 2016 election.

The indictments formed part of an investigation by special counsel Robert Mueller that Trump has denounced as a “witch hunt” designed to undermine the legitimacy of his surprise win over Hillary Clinton.

Democrats, however, said he should cancel the Helsinki summit, arguing the indictments revealed the lengths to which Putin had gone to meddle in the election that brought Trump to power.

In the interview with CBS, Trump said he “might” press Putin to extradite the indicted Russians. Of the summit as a whole, he said: “I’m not going with high expectations” but insisted: “I think it’s a good thing to meet.

“Nothing bad is going to come out of it, and maybe some good will come out,” he said, pointing to other summits he has held with the leaders of China and North Korea. His meeting with North Korea’s Kim Jong Un ended with a decision by Trump to end US-South Korean military exercises, much to the surprise of Seoul and Tokyo. The Kremlin said it considers Trump a “negotiating partner”. “The state of bilateral relations is very bad,” Kremlin adviser Yuri Ushakov said Friday. “We have to start to set them right.”

But US allies and many in Washington are worried about what Trump might conceivably bargain away to Putin. The US president used a stormy G7 summit in Canada to ponder whether it was time to readmit Russia to the club, and move past sanctions imposed over Moscow’s seizure of the Crimea region from Ukraine.

The outlines of what would be a hugely controversial deal have emerged in press reports that suggest Putin is keen to exploit Trump’s desire to pull US troops out of Syria by offering to rein in Iranian influence there.

US recognition of the Crimea grab by Russia in 2014 and an end to the sanctions would be part of the mix.

Putin has less reason to cheer Trump’s imposition of trade tariffs on countries including Russia, and from his decision to abandon a landmark nuclear pact with Iran.

Trump also says he intends to pressure Putin over the rapid growth and modernisation of Russia’s nuclear arsenal.

But for Putin, merely getting Trump to sit across the table counts as “an informal recognition of Russia as a great power”, political analyst Alexei Malashenko said.