Objections from Poland, principally regarding voting rights, were overcome through a compromise in which reductions in the country’s voting power will not be introduced until 2014.
The UK, which had been the other major objector to the treaty, secured a number of opt-outs in areas such as criminal law. Other objections from France, the Netherlands and Denmark also led to compromises.
Sweden’s Prime Minister Fredrik Reinfeldt welcomed the agreement. He said that Sweden had argued in negotiations against raising the bar for new potential members of the EU.
He praised German Chancellor Angela Merkel’s efforts to secure a deal.
“Sweden’s position has been to support Germany,” he said.
“After seven years and tough discussions, we have come to agreement and can now take the work of the union forward and make the EU more effective,” Reinfeldt told a press conference on Saturday.
The deal means that Sweden, which will hold the rotating presidency of the EU in the second half of 2009, could be responsible for installing the new High Representative for Foreign Policy, Defence and Security and a full-time President of the European Council.
The European Union constitution was rejected in referendums in France and the Netherlands in 2005, forcing leaders to go back to the drawing board.