The statement was adopted after a two-day conference in Bled, Slovenia, which ended on Saturday.
Slovene Parliament Speaker France Cukjati told the press that if the accession strategy were to slow down because of problems with the European Constitution, countries applying for membership might become sceptical of the Union.
Today, the conference was joined by parliamentarians from Croatia, Albania, Bosnia-Herzegovina, Serbia and Montenegro, and Macedonia. Croatia was represented by Deputy Parliament Speaker Mato Arlovic.
Over two days, parliamentarians from six EU members advocated continuing with the ratification of the European Constitutions despite the "no" it was given at recent referenda in France and the Netherlands.
The final statement underlined that the EU should open negotiations with Croatia as soon as possible, and supported the EU integration of the rest of the region.
The joint statement also underlined the need to continue cooperating with the Hague war crimes tribunal.
Asked by the press if allegations of recent attempts to persuade Bosnian Serb wartime military commander Ratko Mladic to surrender to the UN court were linked to Belgrade's attempts to join Euro-Atlantic institutions, Serbia and Montenegro Parliament Speaker Zoran Sami said that cooperation with the Hague tribunal was an international commitment.
"All those who committed war crimes or are suspected of them must answer personally, but an entire people must not bear the guilt for that," he said.