The Convention on the Future of Europe has finalised a draft charter for the proposed EU constitution.
However, the 105 delegates at the convention failed to agree on how much power national governments should cede to the European Commission.
Differences in relation to taxation, foreign policy and immigration will be addressed by member states in talks due to begin in Italy in October.
The EU constitution aims to incorporate existing European treaties and streamline the decision-making process when the union expands from 15 to 25 members.
Irish Junior Minister Dick Roche said the final constitution could be completed during Ireland's presidency of the EU.