Germany's top envoy, who is hosting the two-day talks in the western city of Bonn, suggested that the election of President Donald Trump should be a wake-up call for Europe if its wants to prepare for challenges to come.
Foreign Minister Sigmar Gabriel told German daily Frankfurter Allgemeine Zeitung that the European Union needs reform if it wants to be taken seriously by global powers such as the United States, Russia and China.
"We have believed for too long that our way of living is best defended by the Americans," said Gabriel, a reference to Washington's cultural, diplomatic and military dominance of the West after World War II.
Gabriel suggested it was time for Europeans to leave their comfort zone and stand up for their values, if necessary by military means, without relying on America's support. Doing so could help address growing skepticism about the EU that has resulted in a revival of nationalist politics on the continent in recent years.
"Pressure from outside can be quite beneficial," said Gabriel.
Officially, talks among the Group of 20 leading industrialized and emerging economies will focus on the 17 so-called sustainable development goals that the international community agreed to aim for by 2030. Recognizing and preventing future crises, as well as support for Africa, are also on the agenda.
But a flurry of bilateral meetings preceded the summit's official start mid-afternoon.
For many foreign ministers it was the first opportunity to meet with recently confirmed U.S. Secretary of State Rex Tillerson, whose team had set up a base outside Bonn.
The former CEO of oil giant Exxon Mobil met his counterparts from Saudi Arabia, Britain, Oman and the United Arab Emirates in the morning, and an encounter with Russian Foreign Minister Sergey Lavrov was planned later in the day.
Gabriel, meanwhile, indicated that Germany is keen to improve its sometimes tense relations with Russia and China.
Speaking after face-to-face talks with his Chinese counterpart Wang Yi, he said Berlin and Beijing planned to strengthen not just their already close trade ties but also foster cooperation in the areas of education and civil society.