BERLIN -- Foreign ministers of the European Union's founding members on Saturday urged quick negotiations about Britain's departure from the bloc, saying the other 27 countries in the union need to move ahead and think about the future.

"There is a certain urgency ... so that we don't have a period of uncertainty, with financial consequences, political consequences," French Foreign Minister Jean-Marc Ayrault said.

He spoke alongside counterparts from the other five founding members of what has become the EU -- Germany, Italy, the Netherlands, Belgium and Luxembourg.

The leaders also accepted a degree of criticism that the EU in recent times did not show the energy and braveness needed to work together on such important topics as migration, unemployment and terrorism.

German Foreign Minister Frank-Walter Steinmeier also said negotiations on a British exit, or Brexit, should begin "as soon as possible" and added that "intensive European discussions" are needed.

Luxembourg's Foreign Minister Jean Asselborn said he hoped there would be no "cat and mouse" game now and that Britain would invoke Article 50 of the EU charter, which would officially start the exit process.

"There must be clarity," Asselborn told reporters. "The people have spoken and we need to implement this decision."

German Chancellor Angela Merkel, speaking at a different press conference in Potsdam, outside Berlin, also prodded for British action.

"To be honest, it shouldn't take forever, that's right -- but I would not fight over a short period of time," Merkel said.

The British side is much more relaxed. Prime Minister David Cameron is resigning and says his successor, to be chosen by October, should start the formal exit process.

All six foreign ministers agreed that Europe needs to do more to solve pressing issues like the migration crisis, unemployment and security concerns following the terror attacks in France and Belgium.

"We did not have the energy, the power, and perhaps the braveness, to make the necessary decisions and this we must now show in Europe --that we are in a position to make decisions, especially in difficult fields like migration," Steinmeier said.

In a joint statement, the leaders said they need to find ways to better deal with the different levels of ambition in regard to the European integration and that they need to make sure that Europe will be better at fulfilling the expectations of all citizens.

Ayrault urged the remaining 27 EU countries to return to "the spirit of the founders" of European unity, forged to prevent conflict via trade after World War II.

"It is up to us to recreate this spirit," he said, noting all the European countries that subsequently joined after overthrowing dictatorships and embracing democracy.

However, the leaders did not present a concrete plan on how to tackle the union's many pressing issues and how exactly they will react to the citizen's worried and EU-fatigue.

The head of the EU's executive Commission, Jean-Claude Juncker, warned in German daily Bild on Saturday that other countries may also call for referendums to leave the EU.

"The populists will not leave out this opportunity to promote their anti-Europe politics with much noise," he said.

At the same time, he said the consequences the British people may now face could put a stop to such sentiment.

"It should show quickly that Great Britain did better in the EU -- economically, socially and when it comes to foreign politics," Juncker said.

David Rising contributed reporting.