President Donald Trump arrived in Europe on Wednesday for three days of diplomacy that will culminate in a meeting with Russia’s Vladimir Putin, an encounter with the potential to spark global repercussions and political fallout back in the US.

Even his top aides do not know precisely what Mr Trump will decide to say or do when he and Mr Putin meet face to face on Friday on the sidelines of the Group of 20 economic summit gathering in Hamburg, Germany.

And that is what most worries those advisers as well as officials across his administration as Mr Trump begins his second foreign trip as President, stopping first in Warsaw to give an address on Thursday and then heading to Hamburg.

The highly anticipated conversation with Mr Putin is in many ways a necessity, given the critical disputes separating the United States and Russia.

But it also poses risks for Mr Trump, who faces a web of investigations into his campaign’s possible links to Russia, as well as questions about his willingness to take on Moscow for its military aggression and election meddling on his behalf.

The air of uncertainty about the meeting is only heightened by the President’s propensity for unpredictable utterances and awkward optics.

And it is not the only charged encounter awaiting Mr Trump this week.

Donald Trump will meet with Vladimir Putin this week. Photo: Getty

Following North Korea’s launch on Tuesday of an intercontinental ballistic missile, he also faces new pressure to act on a threat from Pyongyang that has long confounded American presidents, and that he has few appealing ways to address.

He is scheduled to meet in Hamburg with President Xi Jinping of China, as he complains that Beijing has not done enough to rein in North Korea.

If Mr Trump’s first foreign trip, in May, was a chance for him to escape turmoil at home – staff infighting, a stalled agenda and the Russia-related investigations – his second will thrust him into the maelstrom. And at the centre of it, Mr Putin awaits.

“There’s a fair amount of nervousness in the White House and at the State Department about this meeting and how they manage it because they see a lot of potential risks,” said Steven Pifer, a former ambassador to Ukraine who has worked for the National Security Council and the State Department.

“There is this grey cloud for the President of the investigations about collusion, so any kind of a deal is going to get the micro-scrutiny of, ‘Is this a giveaway to the Russians?’”

Mr Trump himself does not appear to be troubled by the meeting. He has told aides he is more annoyed by the prospect of being scolded by the German chancellor, Angela Merkel, and other leaders for pulling out of the Paris climate accords and for his hard line on immigration.

Mr Trump’s team said he might bring up Russia’s documented meddling in the 2016 election, but he is unlikely to dwell on it: doing so would emphasise doubts about the legitimacy of his election.

President Trump departs the White House before his trip to Warsaw and Hamburg. Photo: Getty

Aides expect him to focus on matters involving Syria, including creating safe zones, fighting the Islamic State and confronting Mr Putin’s unwillingness to stop the government of President Bashar al-Assad from using chemical weapons against civilians.

Before the meeting between the American and Russian presidents, Secretary of State Rex Tillerson said late on Wednesday that the United States “is prepared to explore the possibility” of expanded co-operation with Moscow in Syria, including a discussion of establishing no-fly zones.

A day before Mr Trump left Washington, the White House announced that the meeting would be a formal bilateral discussion, rather than a quick pull-aside at the economic summit gathering that some had expected.

The format benefits both Mr Putin, a canny one-on-one operator who once brought a Labrador to a meeting with Ms Merkel because he knew she was afraid of dogs, will be able to take the measure of Mr Trump.

President Putin is expected to press Mr Trump to lift sanctions imposed on Russia. Photo: Getty

Mr Trump’s aides are seeking structure and predictability. They hope that a formal meeting, with aides present and an agenda, will leave less room for improvisation and relegate Russia’s meddling in the US election to a secondary topic, behind more pressing policy concerns that the President is eager to address.

Cognisant of the perils, the White House has planned Mr Trump’s itinerary to counter the perception that he is too friendly with Moscow.

The biggest concern, people who have spoken recently with members of his team said, is that Mr Trump, in trying to forge a rapport, appears to be unwittingly siding with Mr Putin.

“You don’t want to come out of there saying, ‘We’re friends, and the enemy is the deep state and the media’,” said Michael McFaul, a former ambassador to Russia.

– The New York Times