Last week, Chancellor Merkel addressed the German Parliament where she said that the issue of climate change will be discussed at the upcoming G-20 Summit in Hamburg, Germany, which will nearly surely include conversations regarding Trump's decision to withdraw the United States from the Paris Climate Agreement.
Before meeting with his counterparts, President Trump has called on numerous global leaders with regard to disputed issues.
Trump was expected to return to the White House Monday evening.
In a pre-summit meeting in Berlin last week, Merkel reemphasized the importance of the Paris accord that fights climate change.
A day before the G20 starts, Trump will head to Warsaw for a meeting of central and eastern European leaders likely to include Hungary's hardline Prime Minister Viktor Orban, who has sparred with western European leaders, especially on the refugee issue.
The U.S.is now described as a "partner" rather than a friend, revealing the tense relations between Germany and the USA since President Trump took office.
Donald Trump, world leaders head to G20 Summit under N Korea shadow
Greenpeace, for example, regards the G-20 as a chance for the leaders to send a strong signal about fighting climate change - despite the Trump administration's decision to pull out of the Paris agreement on reducing emissions. Last week, the USA approved $1.42 billion in arms sales to Taiwan.
It's not yet known if Trump will raise the issue of Russia's meddling during the meeting.
Trump "addressed his concerns", the White House said, about the dispute the Saudis, Egypt, Bahrain and the United Arab Emirates have with Qatar.
Several people were arrested when German police cleared a campsite established to protest the upcoming G20 summit in Hamburg, police said.
The global fight against terrorism, the related, thorny issue of Qatar and growing division between Europe and the United States will feature prominently as world leaders gather in the German city of Hamburg for a potentially stormy summit starting on Friday.
Much of the media focus will be on the first face-to-face meeting between Mr Trump and Russian President Vladimir Putin, as relations between the two nations sour over alleged Russian interference in the 2016 United States election and differing views on Syria and Ukraine.
Beijing's SChina Sea missiles ready for deployment
Department of State. "The United States will fly, sail and operate wherever worldwide law allows", he told USA Today . Navy conducted a "freedom of navigation exercise", or FONOPS, with the maneuver, Fox reported.