“The European Council noted that the Czech Republic cannot complete the ratification process until the constitutional court delivers its positive opinion on the accordance of the Lisbon Treaty with the Czech constitutional order,” the leaders said in a footnote to their final statement at a two-day summit.

Most leaders sought to put a positive spin on the message, noting that ratification of the treaty by other countries would continue and they would review the way forward together with Ireland at their next summit in October.

“I’m convinced our agreement gives a very positive impulse towards the final solution,” Slovenian Prime Minister Janez Jansa, who chaired the summit, told a closing news conference.

The treaty is designed to give the bloc stronger leadership and institutions to cope with recent and future enlargement.

British Prime Minister Gordon Brown said he expected all the other 26 member states to ratify the text and Ireland to come back to its partners with ideas for the way forward in October.

Traditionally Eurosceptical Britain raised EU spirits this week by concluding parliamentary ratification, but a high court judge advised Brown on Friday not to complete the process until he had ruled on a civil suit demanding a referendum.

But French President Nicolas Sarkozy, who inherits the issue when France takes on the rotating EU presidency on July 1 and will visit Dublin next month, pointed to the risk of contagion.

“Ireland is a problem. But if we had a second or a third problem, it would become very difficult to solve,” he told a news conference.

“A renegotiation of the treaty is out of the question. We are not going to redo a second simplified treaty,” he said, noting the Lisbon treaty was itself a boiled-down version of the EU constitution rejected by French and Dutch voters in 2005.

All 27 member states must ratify for it to take effect. The Czechs, whose Eurosceptical center-right Civic Democrats are concerned about national sovereignty, had sought to prevent any call for continued ratification after the June 12 Irish referendum defeat.

Czech President Vaclav Klaus declared the treaty “dead” after the Irish vote and the Senate has referred the text to the constitutional court for a ruling not expected before October.

“We are a democracy — even the head of state is allowed his own opinion,” Foreign Minister Karel Schwarzenberg joked. The independent pro-EU minister said he still thought his country would endorse the text by year-end.

Prime Minister Mirek Topolanek — seen as less keen on the treaty — said on Thursday night: “I am not going to force members of parliament to back Lisbon and I would not bet 100 crowns (4 euros) on a Czech “Yes”.”

The treaty would give EU leaders a long-term president, a stronger foreign policy chief with a real diplomatic service, a more democratic decision-making system and more say for the European and national parliaments.

Sarkozy insisted that without the Lisbon treaty there could be no further enlargement of the Union — a view contradicted by Jansa, Polish Prime Minister Donald Tusk and others.

Austrian Foreign Minister Ursula Plassnik said the EU must keep its word to aspirants for membership in the Western Balkans and Croatia, top of the queue to join, should not become the first victim of the Irish referendum.

Options mooted to resolve the crisis have included offering assurances to the Irish that the Lisbon Treaty will not undermine their cherished neutrality, deprive them of a commissioner in Brussels, make abortions easier or raise taxes — and then asking them to vote again, as happened once before over an earlier EU treaty.

Prime Minister Brian Cowen said he could not speculate on whether Ireland would have another referendum.

Determined to show voters the EU is not paralyzed and is addressing citizens’ key concerns, the bloc’s leaders asked the European Commission to study the feasibility of tax measures to ease the pain of soaring oil prices and report back in October.

EU officials stressed that agreement to study proposals such as Sarkozy’s idea of capping value-added tax on fuel or an Austrian call for a tax on commodity speculation did not mean they would recommend the measures, widely criticized by others.