BRUSSELS, March 26: European Union leaders ended a two-day summit on Friday with a breakthrough pledge to clinch a so-far elusive constitutional deal by mid-June.

The leaders also agreed on an anti-terrorism package creating the bloc's first security chief and pledged automatic aid - including military assistance - to any member state attacked by terrorists.

In a less upbeat mode, the summit recognized that the soon-to-be 25-nation bloc was lagging far behind the economies of the United States and Japan as well as China. Irish Prime Minister Bertie Ahern's success in persuading leaders to stop bickering and start renegotiating the treaty was hailed as a major success of the summit.

Mr Ahern said he would try and secure a deal by the next EU summit scheduled for June 17-18. Talks on the EU constitution collapsed last December amid a bitter struggle over national voting clout which pit Spain and Poland against Germany and France.

It will still be tough to clinch a final treaty but Europe's mood is changing. The devastating Madrid bombing earlier this month, which killed 190 people and injured about 1,800, has forced leaders to focus their attention on more fundamental challenges facing the Union.

Crucially, the surprise victory of Jose Luis Rodriguez Zapatero has broken the deadlock, with Madrid's future leaders pledging a more conciliatory line on EU power-sharing.

Left out in the cold after Spain's shift, Poland is also signalling a willingness to compromise. But euphoria over the constitution was tempered by the blunt admission that EU member states were failing to carry out vital economic reforms agreed four years ago at the Lisbon summit.

The so-called 'Lisbon goals' are a series of economic targets aimed at turning the EU into the most competitive region in world. Approved in 2000, the 10-year-plan calls for the EU to sweep past the US and Japan by 2010.

But carrying out reforms agreed on paper has proven far more difficult than leaders envisaged. EU leaders admitted in a statement that results so far were 'mixed' and that the pace of reforms needed to be speeded up in order to meet the 2010 deadline.