Top European Union officials were hunkering down in Brussels Friday to try to work out what to do next after the shock decision by British voters to leave the 28-nation bloc.

European Commission President Jean-Claude Juncker is hosting talks with the leaders of the European Council and Parliament, along with Dutch Prime Minister Mark Rutte, whose country holds the EU's rotating presidency.

The four will try to agree on a European position on the vote, which could see a member country leave the bloc for the first time ever, ahead of a summit of EU leaders in Brussels starting on Tuesday.

Parliamentary leaders were meeting separately, and European commissioners — the EU's executive body — could hold separate talks later.

EU officials have been aware of the possibility that a British vote to leave might come, but while the possibility of an exit is enshrined in EU law no one is sure how a departure would play out.

The head of the biggest bloc in the parliament fired an early warning shot at Prime Minister David Cameron that Britain should expect no free ride as it negotiates its departure.

"There cannot be any special treatment for the United Kingdom. The British people have expressed their wish to leave the EU. Leave means leave. The times of cherry-picking are over," European Peoples Party leader Manfred Weber said.

He insisted that the exit negotiations "should be concluded within two years."

This insistence on a "hard exit" is aimed at discouraging other countries from wanting to leave the bloc in the belief that they might be able to negotiate a comfortable partnership from the outside.

Many European officials fear the U.K. vote will play into the hands of the far right and left and fuel calls for referendums in other countries.

The exit vote also raises troubling questions about the future of Europe in the wake of the economic crisis, concern about Greece's place in the euro and the EU's inability to manage the refugee emergency.