Spain wants an agreement on the European Union's draft constitutional treaty and will do everything to achieve this, Spanish Prime Minister Louis Rodriguez Zapatero vowed in Warsaw Friday, according to dpa. "We have a treaty which isn't ideal, but it is a treaty which will allow us to develop further," Zapatero said at a joint briefing with Poland's Prime Minister Jaroslaw Kaczynski. After talks with German Chancellor Angela Merkel in Berlin earlier Friday, Zapatero urged Poland's political leaders to "look forward" to "progress" when considering their position on the EU constitution. Poland is the only member of the 27-state EU which rejects the current version of the EU constitutional treaty and may veto further progress on the deal at the EU's upcoming summit in Brussels June 21- 22. It is standing firm firm on its demand that the "double majority" voting system in the existing draft, which Poland claims favours larger countries, be changed to the so-called "square root" system in order to give equal clout to all states, both large and small. On Friday the Polish parliament passed a resolution backing the so-called "square root" voting system. According to a survey by the independent TNS OBOP pollsters published Friday by Poland's Dziennik daily, the majority of respondents also said Prime Minister Kaczynski was right to insist on the "square root" model. Spain's Zapatero is the latest in a string of European dignitaries to visit Warsaw this week in hopes of securing Poland's agreement to the EU's draft constitution at the EU summit in June. French President Nicolas Sarkozy and Austrian Chancellor Alfred Gusenbauer were among other dignitaries who visited Warsaw this week in hope of securing Poland's agreement for the draft constitution. Approved by 18 of the EU's 27 members the bloc's draft constitution hit a wall in 2005 when French and Dutch voters rejected the document in separate referenda.