Italian prime minister Silvio Berlusconi warned on Friday that crunch talks aiming to hammer out a first-ever EU constitution may have to be postponed until next year

The warning, perhaps designed to concentrate the minds of bickering EU leaders, came amid warnings the talks could collapse into a fiasco that would leave the bloc facing crisis as it expands from 15 to 25 countries. Berlusconi, who says it could take a ‘‘miracle’’ to strike a deal at a two-day summit scheduled to end on Saturday, warned that the central dispute on the issue of national voting rights could block accord. ‘‘The vote system is a rock on which the whole deal could run aground,’’ he said. ‘‘If the (negotiations) can’t be concluded by Sunday morning, which is the deadline we’ve fixed, it would be better to continue (talking) than to make a bad deal,” he said. ‘‘We can’t accept a cut-price deal,’’ Berlusconi said, indicating the constitutional debate could stretch into the EU’s Irish presidency next year. The main sticking point at the summit is Spain and Poland’s refusal to give up generous voting rights they secured at a summit three years ago, despite strong pressure notably from EU heavyweight Germany. The summit, scheduled to last two days but which could turn into a marathon haggle through the weekend, aims to agree on a constitution that will streamline the EU’s decision-making process.