European Commission President Jean-Claude Juncker said the future of the EU is not "at risk" despite Britain's decision to leave the bloc.
"We respect and at the same time regret the U.K. decision, but the European Union as such is not at risk," Juncker told the European Parliament in Strasbourg in his annual State of the Union address on September 14.
Juncker said he wanted Britain's exit process to happen quickly "so that our relations with the U.K., which must remain on a friendly basis, can take a new shape."
But he warned that if Britain wanted to retain access to the bloc's single market of 500 million consumers, then it would also have to accept the EU's core principle of freedom of movement of people.
"There can be no a la carte access to the single market," he said.
British Prime Minister Theresa May has said formal EU talks will not begin until 2017.
Juncker also said Brexit offered a warning that the EU faces a battle for survival against nationalism in Europe, saying “fragmentation” in the continent was “leaving scope for galloping populism."