"The strategic character of Chinese-German relations is steadily gaining in importance", Xi said in an op-ed article published Tuesday in German newspaper Die Welt, citing data showing that China became Germany's most important trade partner in 2016.
U.S. President Donald Trump and Russian President Vladimir Putin will also meet at the summit, and Germany will try to push climate change and free trade to the top of the agenda.
As for the USA deployment of the Terminal High Altitude Area Defense (THAAD) system in South Korea, Xi and Putin said the move concerns the strategic balance in the region.
German Chancellor Angela Merkel says she expects the Group of 20 leading economies to broadly agree on tackling worldwide terrorism at a summit in Hamburg later this week.More news: Venus Williams At Fault In Fatal Car Crash
Chinese state media said Xi told also Trump "negative factors" have affected U.S.
Hamburg will host the G-20 summit on July 7 and July 8.
"The discord is obvious and it would be dishonest to paper over the conflict", she said.
In the article, Xi pointed out that people-to-people exchanges play an important role in elevating China-Germany relations to a higher level.More news: House Passes Bill Defunding Sanctuary Cities
In the age of Trump, the more Merkel stands up to other world leaders, the more German voters seem to support her. "So we need to deal with China's demands in a way that brings harmony and advantages for both sides".
She said Trump is at odds with other global leaders on some issues, perhaps most notably in pulling the United States out of the 2015 Paris worldwide agreement to curb greenhouse gas emissions in the coming years. "We hope that the G-20 will continue to uphold the great goal of an open world economy".
The Trump administration is also pressuring G20 nations to take steps to reduce global steel oversupply and other distortions in that market.More news: Shady deal: Trump prepares concessions for Putin at first G20 meeting