BBC News Online profiles the leading contenders for the post of president of the EU Commission:
Jose Manuel Durao Barroso, Portuguese PM
Durao Barroso is a supporter of the US-led war in Iraq
Portugal's prime minister, at 48, leads a centre-right coalition and has served as foreign minister of his country. He is fluent in several European languages.
His support of the US-led war in Iraq had made him less attractive to some of the large European countries such as France and Germany but he now has the support of German Chancellor Gerhard Schroeder.
He is unpopular at home after an austerity programme to reduce the country's budget deficit under EU's Stability and Growth Pact.
Correspondents say he has grown a thick political skin, sticking to his views whatever public opinion suggests.
Bertie Ahern, Irish PM
Mr Ahern says he does not want the Brussels job
Widely admired among fellow leaders for his handling of current Irish EU presidency.
The 52-year-old is leader of the centrist Fianna Fail party and when he took office as Irish prime minister was the youngest person to hold that post in modern Irish history.
But he says he does not want the Brussels job.
Some diplomats say he might be persuaded to change his mind once Ireland relinquishes the EU chair at the end of June. He speaks no French.
Antonio Vitorino, EU Commissioner
Antonio Vitorino is widely respected but little-known outside Brussels
Seen as a dark horse in the race, the 46-year-old Portuguese is widely respected as European commissioner for justice and home affairs. He is fluent in several languages, including French and English.
But he is a socialist who does not represent the centre-right majority of the newly-elected parliament - and has no prime ministerial experience, although he is a former defence minister and deputy prime minister.
He is also little-known outside Brussels and Portugal. Another handicap is that the centre-right leads most EU governments and parliament.
Jean-Claude Juncker, Luxembourg PM
Jean-Claude Juncker is a hugely experienced politician
Overwhelmingly re-elected in June 2004 by Luxembourg's 450,000 people, Mr Juncker - a Christian Democrat - has repeatedly said he would rather stay on in his job than run the EU executive and now appears to have withdrawn from the race.
However, at 49, this chain-smoking bon vivant is a hugely experienced politician and the EU's longest-serving leader, who combines the job of prime minister with that of finance minister.
He has strong communication skills, speaking fluent French, German and English, as well as his native Luxembourgisch. But he would be the third Luxembourger to hold the job, a distinction that no other EU country has achieved.
Javier Solana, EU foreign policy chief
Mr Solana said it would be hard to turn down the job if offered to him
The 61-year-old EU foreign policy chief is a Spanish socialist and as such faces the same obstacles to his appointment as other socialists.
He is expected to be reappointed in his current job with a view to becoming first EU foreign minister when the constitution is ratified.
However, he might just be a compromise candidate, and he has said it would be hard to turn down the job if he was asked to take it.
Pat Cox, European Parliament President
Pat Cox is a former television presenter
The outgoing European Parliament president is a 52-year-old Irish
He is an articulate former television presenter who raised the EU assembly's profile and won cross-party respect. He speaks good French.
However, Mr Cox has never run a government or major administration.
Two of the contenders have now said they will no longer be seeking the job.
Chris Patten, EU Commissioner
Chris Patten wants closer EU-UK integration
A pro-European British Conservative and former governor of Hong Kong. Considered a strong public speaker, and someone who could help fight the tide of euroscepticism in Britain and win a referendum on the EU constitution.
The 59-year-old has long been critical of what he considers the endemic waste and fraud of the European Union's foreign aid programmes and the slowness of Brussels bureaucracy.
As commissioner for external relations he has been closely involved in recent attempts to define and refine what he calls "a common foreign and security policy", as well as working alongside Nato.
But he withdrew from the race after strong opposition from France and Germany.
Guy Verhofstadt, Belgian PM
Belgian PM Guy Verhofstadt enjoys support from France and Germany
The boyish-looking 51-year old, with his distinctive gap teeth, is a liberal. He has enjoyed the full support of Germany and France, not least for his federalist views on European integration and tax harmonisation.
But the Belgian PM alienated the UK, Italy and Poland - all three part of the US-led coalition in Iraq - by organising a mini-summit on European defence last year, together with the other opponents of the war. It became known as the "chocolate-makers' summit".
Mr Verhofstadt suffered a setback, however, when his party came third in the recent Belgian regional elections, and he announced the withdrawal of his candidacy after European leaders failed to find agreement on the issue at the Brussels summit.