French President Francois Hollande Thursday said that France and Germany needed to "set a course" for Europe in the aftermath of Britain's decision to leave the European Union.
"Our two countries are essential so that all of Europe can move forward," Hollande said after a meeting in Paris with newly-elected German President Frank-Walter Steinmeier.
"France and Germany now have the clear responsibility to set a course for Europe," Hollande said.
British Prime Minister Theresa May on Wednesday formally notified Brussels of Britain's intention to leave the European Union with a letter that triggered two years of Brexit negotiations.
Paris and Berlin should "give our respective peoples a vision so that we can be fully engaged to build the Europe of the future," Hollande said.
The alliance between France and Germany has long been the key relationship at the heart of the EU's internal politics.
Steinmeier, whose visit to Paris is his first foreign trip since being sworn in last week, joined Hollande in stressing the importance of the European project.
"Germany and France have a greater - an even greater - responsibility to protect European integration," he said.
Hollande backed European Council President Donald Tusk's position that the conditions for Britain's departure from the bloc would have to be agreed before negotiations started on any future relationship.
British leaders had hoped to start discussing future trading terms in tandem with the talks on how the country would end its EU membership, which are expected to take two years.
"We will also have to resolve the very important issue of the European nationals in the United Kingdom and British citizens in our countries," Hollande noted.
According to British government research, there are probably about 3 million EU citizens living in Britain and 1.2 million Britons living in other EU countries.
Many of them are at risk of losing their rights to live and work where they now reside unless Britain and the EU strike a deal on the issue.
Hollande had spoken to May by phone earlier in the day. According to a statement from the Elysee Palace, he "reminded" the British premier that the Brexit talks should take place "in a clear and constructive manner, in order to remove uncertainty and fully respect the rules and interests" of the EU and its remaining member states.
After his meeting with Steinmeier, Hollande warned that neither France nor Germany were themselves immune from "the temptation ... of turning inwards" and the "nationalist trap."
The Socialist president, whose term of office ends in May, has in recent months repeatedly warned against the rise of extreme nationalism, not least in the elections for his own successor.
Far-right candidate Marine Le Pen is neck and neck with centrist Emmanuel Macron ahead of April's first round of voting, although opinion polls suggest Macron, a strong supporter of the EU, should beat the National Front leader comfortably in the decisive run-off vote on May 7.
Le Pen has hailed Brexit and says that if elected, she will take France out of the euro currency and the Schengen border-free zone, as well as holding a referendum on leaving the EU altogether.