"Welcome to Hell". That's the greeting for the leaders of the 20 major industrial and developing economies from anti-capitalist protesters in northern German city of Hamburg who aim to disrupt the G20 summit, already rife with tensions over trade and climate change.
Thousands of protesters from around Europe were pouring into the port city to join big demonstrations later. Police expected around 100,000 protesters in Hamburg, some 8,000 of whom are deemed by security forces to be ready to commit violence.
This poses a challenge for those tasked with securing the July 7-8 summit of leaders of the world's 20 biggest economies, hosted by Chancellor Angela Merkel, who face tough talks on divisive issues including trade and climate change.
While protests so far have been largely calm, city police chief Ralf Martin Meyer told ZDF television: "We are skeptical as to whether this evening and tonight will remain peaceful."
On the sidelines of the summit, Merkel will meet leaders including President Recep Tayyip Erdoğan and Trump, who in Poland called again on NATO partners to spend more on defense and said he would confront the threat from North Korea.
Trump will also have his first session with Russian President Vladimir Putin after the U.S. leader called Russia's behavior "destabilizing", a description the Kremlin rejected.
Merkel, who is running for a fourth term in a September election, stressed on Thursday that she was committed to an open international trading system, despite fears of U.S. protectionism under Trump.
"We're united in our will to strengthen multilateral relations at the G20 summit...We need an open society, especially open trade flows," she said in Berlin.
Many other groups are calling for peaceful protests, and are pushing the G20 leaders for action on climate change, to address economic disparities in the world and a wide array of other issues. Some are even calling for the dissolution of the G20 itself so that the United Nations becomes the platform for such discussions.
On Wednesday more than 7,000 mainly young and beer-drinking revelers staged a march waving placards denouncing capitalism and G20 leaders.
But a fire overnight at a luxury Porsche car dealership in the north of the city that damaged eight vehicles could be a foretaste of what's to come. Police said they were investigating whether it was an arson attack linked to the summit.
Locals are unhappy with Merkel's decision to hold the summit in the center of Germany's second-largest city to show healthy democracies could tolerate protests, as they are worried about property damage by leftist militants.
After Hamburg authorities curbed camping by protesters, the St Pauli football club offered 200 sleeping places in their stadium as "a clear signal for human rights, freedom of expression and the right to demonstrate".
Up to 20,000 police officers will be on duty to watch over the main demonstration, dubbed "Welcome to Hell" by the alliance of anti-capitalist groups who organized it.
Protesters say the G20 has failed to solve many of the issues threatening world peace, including climate change, worsening inequality and violent conflicts.
Tens of thousands were expected to gather at the fish market in the borough of St Pauli - known for its red light district - at 1400 GMT, around the same time as Trump's Air Force One jet is due to land in Hamburg. They will then march north to the heavily secured summit venue.
"It's ridiculous that police say some of us are violent when starting tomorrow the leaders of the world's largest weapons-exporting and importing nations will be arriving in our city," said Stefan Hubert, a 32-year-old graphic designer who came to the protest on Wednesday with three friends.
Holding a placard reading, "Make love great again!", a play on Trump's "Make America Great Again" campaign slogan, he added: "This summit is a waste of money that could be better spent on deploying more boats to stop migrants fleeing war and hunger from drowning in the Mediterranean."
There is irony in the protesters' dislike of Trump. The U.S. president and anti-capitalist activists have something in common: distrust of globalization.
Yet Trump was in Hamburg to push for trade rules that benefit America, including steel makers facing tough competition from China, while the protesters were demanding more rights for the poor regardless of where they live.