German Chancellor Angela Merkel has stood by her suggestion that Europe can no longer rely entirely on the US and declared that Germany and China can work together to help calm the world's problems.
Mrs Merkel is hosting the G20 summit on Friday and Saturday in Hamburg.
The gathering should make for a challenging combination of world leaders, with US President Donald Trump, Russian leader Vladimir Putin and Turkish President Recep Tayyip Erdogan attending, and major protests are expected.
Welcoming Chinese President Xi Jinping to Berlin, Mrs Merkel said their pre-summit meeting was "a good opportunity to expand and broaden our extensive strategic relations".
"It is a great pleasure for us to welcome you here today at a time of turmoil in the world, when China and Germany can make a contribution to calming down this turmoil somewhat," Mrs Merkel said.
The G20 summit comes amid unease in Europe about the Trump administration's "America First" approach to trade and other issues.
After her last encounter with Mr Trump in late May, Mrs Merkel said: "The times in which we can fully count on others are somewhat over, as I have experienced in the past few days."
Asked in an interview with weekly Die Zeit whether she would repeat that comment, she replied: "Yes, exactly that way.
"It is, for example, open whether we can and should in the future rely on the US investing so much as it has so far in the United Nations' work, in Middle East policy, in European security policy or in peace missions in Africa."
Mrs Merkel also held a pre-summit meeting last week with the event's European participants, who underscored their backing for the Paris accord to combat climate change.
She reiterated that the Trump administration's decision to withdraw from the Paris agreement was "extraordinarily regrettable" and noted that many US states and cities want to continue participating.
Hamburg is a famous hotbed of left-wing protest in Germany and anti-globalisation activists have registered the slogan "G20: Welcome to Hell" for their protests on Thursday.
"We are calling on the world to make Hamburg a focal point of the resistance against the old and new capitalist authorities," said the organisers, who have ties to the Rote Flora squat, a centre for radical leftists where police have clashed frequently with protesters. The site is less than a mile from where the G20 leaders will be meeting.
Incidents in recent weeks believed to be linked to the summit have seen police cars burned and train lines sabotaged, and authorities in Hamburg and nearby Rostock have confiscated improvised weapons like fire extinguishers filled with flammable liquid, material to build petrol bombs, baseball bats and other items in several raids.
Police clashed with hundreds of protesters on Tuesday night, using pepper spray and water cannons to eventually bring the crowd under control.
The Welcome to Hell demonstration is one of dozens of protests registered under a variety of themes - including a far-right pro-Trump rally - with more than 100,000 demonstrators from across Europe and beyond due to take part.
Officials expect 8,000 from Europe's violent left-wing scene, and have been tracking known activists coming in from Scandinavia, Switzerland, Italy and elsewhere, said Hamburg police chief Ralf Martin Meyer.
On Wednesday, hundreds of people painted like clay figures moved slowly and silently through the streets of Hamburg to protest against the summit.