The two-day summit is pondering how to deal with Ireland's "no" to the Lisbon Treaty in last week's referendum. The other EU member states, with the possible exception of the Czech Republic, still strongly support the treaty and want to see it adopted despite the Irish veto.
For instance, Britain, traditionally the member state most opposed to further European integration, ignored the referendum result and approved the treaty this week, becoming the 19th state to do so.
Some political leaders say it would be simplist to declare Europe a "two-speed" entity, in which those countries that want to press ahead do so, and those who don't are left behind. However, German Chancellor Angela Merkel cautioned about taking that road in comments on June 19. She said the EU needs the Lisbon Treaty, but rejected the notion that Ireland could be excluded.
"We must ensure that treaties in the European Union are brought forward unanimously," she said. "There is no other way, no matter how tedious that might be. Unanimity is a prerequisite because member states are the masters of the treaties and, therefore, every individual member state must give its approval."
In comments ahead of the summit, EU Trade Commissioner Peter Mandelson urged the union to put its case for the treaty more vigorously. He said Europe is being too "defensive" and "defeatist" and that it should have gone on the offensive for the treaty in Ireland, rather than let opponents spread "misapprehensions" about it.
Irish Prime Minister Brian Cowen sounded like he was on the defensive when he arrived in Brussels. His government has been blamed for a poor campaign to gain a "yes" result for the treaty. He said Ireland cannot be rushed into any new move.
"It is far too early yet for anyone to put forward proposals," Cowen said. "I fully accept that we will need to work intensively in the coming months to identify what possible solutions may be available to us."
European Commission President Jose Manuel Barroso said the EU must not be paralyzed by the Irish result, saying it must must press ahead with energy saving and climate change policies to counter record oil prices.
But in a cautionary remark directed at Cowen, he noted there are very limited chances to reopen the treaty to make it more palatable to Irish voters.
"It will be very difficult, extremely difficult, to get any institutional change regarding the text of the Lisbon Treaty as it was approved," he said.
Barroso earlier told the European Parliament that the summit will consider measures to help those sections of society most affected by soaring fuel costs, but he said governments should not interfere as their economies adapt to the reality of higher oil prices, which he said are here to stay.
In her comments to the Bundestag on June 19, Merkel supported Barroso's line.
"In our view, financial policy intervention, which is being discussed again and again, and which ultimately constrains necessary adjustments, should be avoided," she said.
The EU has come under criticism in some quarters for not reacting to the series of big demonstrations by truck drivers, fishermen, and farmers who say they cannot live with such high fuel costs.