HAMBURG, Germany (AFP) — US President Donald Trump and Russian leader Vladimir Putin shook hands as they met for the first time Friday at a G20 summit marred by violent protests and a rift between America and its Western allies over climate change and trade.

 The handshake in Hamburg came hours before the brash property tycoon and the ice-cool ex-KGB agent were due to hold a blockbuster bilateral that promises to be dissected frame by frame for any sign of rapprochement or estrangement.

 “I look forward to all meetings today with world leaders, including my meeting with Vladimir Putin. Much to discuss,” Trump wrote on Twitter.

 Asked if Putin felt the same about the talks, Kremlin spokesman Dmitry Peskov said: “Affirmative”.

 Their meeting, say analysts, is of vital importance for issues ranging from the North Korean crisis and conflicts in Syria and Ukraine to US-Russian disarmament treaties, world trade and global warming.

 “While Trump’s pro-wrestling approach is showy, bombastic and impulsive, Putin thrives on judo’s discipline and mental toughness, where a core technique is to keep an opponent off-balance and exploit his weakness,” noted Derek Chollet from think-tank German Marshall Fund.

 “How these contrasting styles of machismo interact… will likely be the defining feature of their relationship.”

Their meeting comes on the sidelines of what is expected to be the most fraught G20 summit in years.

 Trump’s “America First” approach on trade and climate-sceptic stance are testing the relationship with longstanding allies, especially in Europe.

 And his tough response to North Korea’s missile programme — an issue where Russia and China are urging calm — throws a further volatile ingredient into the mix.

 End ‘destabilising’ action

 On the presidential election campaign trail last year, Trump said he hoped relations with Putin could be rebuilt after Russia’s acrimonious ties with his predecessor Barack Obama.

But Moscow faces mounting accusations that it interfered in the election to help propel Trump into the White House. As a result, Trump faces pressure at home and from US allies to take a combative tone.

 In a key speech in Warsaw on Thursday, Trump fired a rare salvo of criticism at Russia, but did not name Putin specifically.

 “We urge Russia to cease its destabilising activities in Ukraine and elsewhere, and its support for hostile regimes — including Syria and Iran — and to instead join the community of responsible nations in our fight against common enemies and in defence of civilisation itself,” he told a cheering crowd of about 10,000 people.

A White House source confirmed to AFP that Trump will be joined at the meeting only by Secretary of State Rex Tillerson and a translator, an extraordinarily small cast list that raised concerns among experts.

 “Neither Tillerson or Trump have any experience of foreign policy. That is one reason why they need pros in the room when meeting Putin,” said Thomas Wright of the Brookings Institution.

 Storm over climate

 North Korea’s successful test of an intercontinental ballistic missile this week also casts a dark shadow over the US leader’s first G20 summit.

Trump had warned Thursday that Pyongyang’s military sabre-rattling would bear

 “consequences”, saying he was considering a “severe” response to its “very, very bad behaviour”.

 After repeatedly urging Beijing to ratchet up the economic pressure on North Korea, Trump will hold what promises to be a testy meeting with Chinese President Xi Jinping on the G20’s sidelines.

 Beyond the complex diplomatic waltz, the US leader also faces tough talks in the main G20 conference room, where a united front is forming against his dismissive attitude to global warming.

 Trump may have vowed to pull the US out of the 2015 Paris climate protection accord, but G20 host German Chancellor Angela Merkel stressed that “many many other countries want to go on implementing” it.

 “We are not going to paper over the differences but rather, we will call discord discord,” said Merkel.

 British Prime Minister Theresa May said world leaders will redouble efforts over the two-day summit to persuade Trump to rejoin the Paris deal.

 “I believe the collective message that will be given to President Trump around this table will be the importance of America coming back into that agreement, and I hope we will be able to work to ensure that can happen,” she told the BBC.

 But the timing of Trump’s meeting with Putin — expected to begin 15 minutes after G20 leaders start their afternoon session on climate change — has been viewed as a sign of the US leader snubbing the issue.

 Cars torched

 Outside the heavily-guarded conference hall, tensions were also high with police clashing with demonstrators again early Friday following a night of running battles that left more than 100 police officers injured.

Beginning early Friday, activists torched more cars, smashed shop windows, fired flares at the police helicopters and even slashed tyres on vehicles belonging to the Canadian delegation.

Small groups played cat-and-mouse with the 20,000 police on duty to try and stop the leaders even getting to the summit venue.

“It’s a total catastrophe that a minority can just riot like this,” local resident Munch told AFP “These idiots have nothing better to do than to demonstrate. They have to be moved out.”