European Union (EU) leaders on Saturday launched negotiations on a new treaty, successfully ending a fraught three-day summit on reforming the 27-nation bloc.
Leaders clinched the hard-fought deal after Poland accepted an 11th-hour proposal delaying Warsaw's implementation of a new voting system until 2017.
Britain, which came to the meeting with several "red lines", secured key concessions on keeping its national powers in justice and police affairs and in restricting the impact of a new legally binding fundamental rights charter on British legislation.
"It was not easy but this shows that Europe comes together at the end," said German Chancellor Angela Merkel, who chaired the meeting marked by high-drama brinkmanship.
Merkel said the deal could be criticized for certain shortcomings, but insisted: "What counts is that we are moving. We have a detailed and clear mandate for an inter-governmental conference" on treaty reform.
The EU decision sends a "good message" about Europe, said French President Nicolas Sarkozy.
Outgoing British Prime Minister Tony Blair said he had won on most of Britain's key demands, adding: "This deal gives us a chance to move on."
The summit deal sets firm guidelines for EU negotiations on an amended treaty, expected to start in autumn.
Once ratified by all 27 EU governments, the new treaty will replace an earlier draft version rejected by French and Dutch voters in 2005.
Officials say the new rulebook is needed to adapt EU institutions and decision-making to the realities of an expanded union.
Explaining the difficulties of hammering out a compromise that could satisfy all 27 states, Merkel said she aimed for a deal that did not leave any country feeling isolated.
"No one can go home and feel that they have been put in a corner," said Merkel, adding that while Poland and Britain had specific claims, she also had to cater to the 18 countries that had ratified the earlier constitution and did not want to "make many sacrifices" by diluting the text.
Polish President Lech Kaczynski said Warsaw had made a big effort at the summit and as a result Poland no longer stood alone.
But Luxembourg's long-serving Prime Minister Jean-Claude Juncker, a strong defender of the now defunct constitution, admitted the final compromise was not satisfactory.
The original constitution would have been much better, said Juncker, adding that the new amended version was actually a "complicated simplified" treaty.
The summit deal addresses Polish demands for upgraded voting rights by giving Warsaw until 2017 to change from the current voting system, agreed to in Nice in 2000, to a "double majority" method under the new treaty.
The Nice formula gives Poland 27 votes, almost on par with big EU states Germany, Britain, Italy and France, which have 29 votes each.
Other EU states, however, will switch to a double majority voting system in 2014. This requires that EU decisions be taken with the support of 55 per cent of member states, representing 65 per cent of the population.
Poland rejected the double majority scheme, arguing that it gives too much clout to the EU's bigger states like Germany.
Discussions got off to an acrimonious start Thursday after Polish Prime Minister Jaroslaw Kaczynski linked his demands for more voting clout to his country's harsh treatment at the hands of Nazi Germany during the Second World War.
Kaczynski said Poland would have had a larger population were it not for heavy losses of human life during the war.
Although President Kaczynski, the premier's less confrontational twin brother, represented Poland at the summit, tensions increased Friday after Poland once again vetoed German offers of compromise.
Angered by Poland's hard-line stance, the normally low-key Merkel, known for her success in forging difficult compromises, used more heavy-handed tactics to get Warsaw on board.
In an unusual show of brinkmanship, the German chancellor warned she would launch treaty negotiations even if Poland refused to join the talks.
However, in a last-minute bid to salvage the summit, Sarkozy, Blair and Juncker made a joint telephone appeal to Prime Minister Kaczynski to try and win acceptance of the new compromise.
In a concession to Britain, the negotiating mandate made clear that the EU's charter on fundamental rights would not apply to Britain's labour legislation.
In addition, as demanded by Britain the treaty will not refer to the appointment of a first-ever EU "foreign minister" but to a "high representative for foreign and security policy".
Britain claimed that the title of foreign minister would give the impression that national governments were ceding sovereignty on foreign policy to the EU.
Blair also secured opt-outs on participating in some decisions on EU justice and police affairs and social security policy.
EU officials said the elimination of a key reference in the treaty preamble to the bloc's commitment to "free and undistorted competition" would not have legal implications.
Merkel has said once negotiations are completed at the end of 2007, the new treaty will enter into force ahead of elections to the European Parliament in summer 2009.