The request comes a week before an EU summit when the European Council is expected to announce a date for the start of talks with Croatia on membership in the bloc.
Senior HSS official Josip Friscic said at a press conference in Zagreb that he expected a positive response from the European Council to Croatia's aspirations to become a full member of the European Union, but that domestic problems in Croatia might slow the country's progress.
HSS vice-president Ljubica Lalic said that the party would present the proposal at a meeting of the chairmen of parliamentary clubs on Monday, and that such a declaration would lend greater credibility to the unity of views on Croatia's EU membership bid.