European Union leaders have begun a two-day summit that is expected to be marked by hard bargaining over the bloc's first-ever constitution, Iraq and plans to kick-start economic growth throughout the EU.

Leaders of the current 15 member states and the 10 that will join next year will discuss such contentious proposals as replacing the bloc's rotating presidency with a full-time executive and changing voting arrangements to give more populous countries greater weight in EU decision-making.

They will also take up burning international issues like the Middle East conflict and Iran's suspected nuclear capability. Iraq's future will also figure prominently in the debate.

The leaders are also expected to debate an initiative to revive economic growth through massive spending on public works and research projects. But conservatives are insisting that spending not exceed the EU's budget deficit limits of three percent of Gross Domestic Product.