The six founding nations of the European Union on Tuesday stressed their commitment to seek an "ever closer union" at a time of deep rifts among the current 28 member nations on the way ahead and Britain's impending referendum whether to stay in the bloc.

The foreign ministers of host Italy, France, Germany, the Netherlands, Belgium and Luxembourg said in a joint statement Tuesday they reconfirm their "strong commitment to Europe and the European project and invite all other member states to join."

Such momentum goes against the terms British Prime Minister David Cameron will be looking for at next week's EU summit, where he will seek to obtain reform commitments to give Britain a more independent say in its affairs and specifically reject a closer union.