The failure to elect a president has raised fears that EU leaders may also fail to agree on a new constitution when they reconvene their talks on Friday.
The leaders could not even agree on one of at least eight names in the frame to take over from current president Romano Prodi for leadership of the Commission for the next five years.
"We have not as yet succeeded in doing that," Irish Prime Minister Bertie Ahern, whose country holds the rotating EU presidency, told a news conference after the talks ended.
"Obviously we have to try to see if we can find a consensus," he said. "We are not in that position. I'm afraid it's going to be a long day tomorrow as well."
Diplomats said the standoff had reopened bitter divisions
within the 25-nation bloc between supporters and opponents of the US-led war in Iraq, pitting supporters of a more federal EU integration against those who want a Europe of nation states.
Heavyweights France and Germany remained firmly in favour of Belgian Prime Minister Guy Verhofstadt, whom Britain had made clear on Wednesday it would not accept at any price.
Germany wants Italy and other
members to agree to Verhofstadt
European conservatives weighed in on Thursday by proposing
the EU's external relations commissioner Briton Chris Patten in the expectation that France and Germany would reject him,
Verhofstadt and Patten thus effectively neutralising each other.
One EU diplomat had earlier said failure to agree on a name could sour the mood so badly that leaders may be unable to build on positive steps made towards the bloc's first constitution.
"If there is no result (on the Commission president) and a
really bad atmosphere, there may not be a deal on the treaty," he said, adding that France and Germany could be deliberately tough in Friday's talks after suffering defeat on Verhofstadt.
Narrowing the list
But Ahern denied this, telling the news conference: "I don't
think it's a question of recrimination".
He said he had eight or nine possible candidates, but had
not formally put forward any of them as he did not yet believe any could achieve the necessary support. However, he said the field had narrowed down to about half of the original list.
Late additions to those in the frame included Irish businessman, former commissioner and former world trade chief Peter Sutherland, and Portuguese Prime Minister Jose Manuel Durao Barroso, but there was no obvious frontrunner.
Despite the presidency row, the EU leaders had quietly edged
closer to a deal on the constitution as they tried to rebuild
public confidence in the bloc following mass abstentions and
eurosceptic gains in European Parliament elections last week.
Ireland said it was "closing in" on agreement on a first constitution after it put forward proposals to narrow differences over voting powers, the bloc's battered budget rules and policy areas where national vetoes will remain.
Ahern said he would make final proposals on Friday to answer
remaining objections on the treaty, which was designed to improve decision-making and give the enlarged bloc a fresh start.
Poland and Spain, whose stand on voting rights sunk a deal
in December, voiced hope that they could agree to a text this time round.
Britain, although it vowed to protect its national veto in some areas, said a deal was more likely than not.
"There is a unanimity that we cannot leave Brussels without
a constitutional text," said Spanish Foreign Minister Miguel
Six months ago, Spain and Poland fought to retain a deal
they won in the 2000 Nice Treaty, which gave them almost as much power as Germany with less than half its population.
One question was whether British Prime Minister Tony Blair
and Polish Prime Minister Marek Belka, punished even more
severely than other leaders in the European assembly vote, felt in a strong enough domestic position to accept compromises.
Blair has gambled on calling a referendum to ratify the
constitutional treaty and demanded that EU leaders meet his "red lines" to maintain national vetoes on decisions on tax, social security, foreign policy and criminal justice.
Dublin proposed raising the proportions of member states and
population required to approve most decisions.
This so-called "double majority" would now require 55%
percent of EU member states representing 65% of the
population for decisions compared with the 50% and 60%, figures respectively that were initially proposed.