The European Union will quickly appoint its first long-term President and a powerful foreign policy chief after ratifying a treaty on Tuesday to give the 27-country bloc more influence on the world stage.
Czech President Vaclav Klaus signed the treaty after his country's constitutional court threw out a legal challenge, ending eight years of wrangling that held up reforms to make the EU function better.
"President Klaus's decision marks an important and historic step for all of Europe," British Prime Minister Gordon Brown said.
"Today is a day when Europe looks forward, when it sets aside years of debate on its institutions, and moves to take strong and collective action on the issues that matter most to European citizens: security, climate change, jobs and growth."
The EU, a political, economic and trading bloc representing nearly 500 million people, must put aside deep divisions if it is to increase its influence and match the rise of emerging powers such as China following the global economic crisis, political analysts say.
EU leaders hailed Mr Klaus's ratification as a vital stage in a long journey to revamp the Union following the accession of 12 new member states in 2004 and 2007, most of them from former communist east Europe, which has complicated decision-making.
The treaty needed the approval of all member states to go into force and only the Czech Republic had been holding out since Irish voters backed it at the second time of asking in September. The treaty replaces a planned EU constitution, abandoned when Dutch and French voters rejected it in 2005.
"Today's development means that the long saga of the Lisbon Treaty is nearing a welcome end, and that the welcome reforms which it contains will now be implemented in the very near future," said Irish Prime Minister Brian Cowen.
Mr Klaus said he opposed the treaty because it would take away national sovereignty.
He signed reluctantly after pressure from other EU leaders but secured a deal giving the Czech Republic an opt-out from a rights charter attached to the treaty, to shield Prague from property claims by ethnic Germans expelled after World War II.
"With the Lisbon Treaty taking effect, the Czech Republic will cease to be a sovereign state, despite the political opinion of the Constitutional Court," Mr Klaus said.
The treaty creates a President to chair the Council of EU heads of state and government for a renewable term of two and a half years and increases the powers of the foreign policy chief. It is due to go into force on December 1.
Sweden, which holds the EU's collective presidency, said it would call a summit soon to discuss the appointments.
This will probably take place this month, before an already scheduled EU summit on December 10-11.
The appointments will allow European Commission President José Manuel Barroso to make nominations to the EU executive, a powerful regulatory body which groups representatives of all the member states and is being renewed following his re-election.
European Parliament President Jerzy Buzek said the assembly would be ready to hold approval hearings quickly on the candidates for the Commission posts - all candidates for the Commission need the Parliament's support.
This could avoid a political vacuum in which the departing Commission served for a long time on a caretaker basis.
The EU now faces horse-trading over the appointments, in which Mr Barroso will try to balance out the member states' interests and influence as he makes his choices. Most countries will fight hard for one of the top economic portfolios.
Former British Prime Minister Tony Blair's chances of becoming EU President have faded. Belgian Prime Minister Herman Van Rompuy has emerged as a possible compromise candidate and Dutch Prime Minister Jan Peter Balkenende could also fit the bill.
Candidates for the foreign policy chief job include British Foreign Secretary David Miliband, EU Enlargement Commissioner Olli Rehn and former Austrian Foreign Minister Ursula Plassnik.