European Union leaders signed a new treaty on Thursday that would give the 27-nation bloc a long-term president and streamline its decision-making process.

The treaty — a slimmed-down version of an abortive European Constitution — would provide for a more powerful foreign policy official who will lead EU strategy, and scrap the rotating six-month presidency in favor of a maximum five-year term for a president elected by the members.

More decisions would be taken by majority vote, eliminating the need for unanimous endorsement, which in the past has stymied the bloc's efforts to present a united front.

The Lisbon Treaty was endorsed by the EU's 27 leaders two months ago and will come into force after it is ratified by all member states. The aim is to complete that process by 2009.

Unlike the failed constitution proposal, which was derailed by the 'no' votes of French and Dutch voters two years ago, the treaty will not go to referendums in 26 of the member states. Only Ireland will give the citizens a chance to vote on it.

The leaders' refusal to hold referendums has brought Europe-wide protests. The others say they will ratify the document in their parliaments.

The agreement follows years of unease among European Union citizens about how much sovereignty they should surrender to centralized rule. The treaty's detractors claim EU governments dare not put the document to a vote because they fear a majority of their people do not want it.

"Europe was blocked, not knowing how to move forward, and we found the solution with this treaty," said Portuguese Prime Minister Jose Socrates, the ceremony's host. His country holds the current six-month presidency.

Under the treaty, the number of European commissioners in the EU executive office is to be cut from 27 to 17 on a rotating basis, part of an attempt to make the EU less unwieldy after its expansion to include Eastern European countries.

In an effort to stress the EU's democratic credentials, the European Parliament is given more power, and can modify or reject proposed EU legislation.

"By resolving its institutional matters, Europe is readying itself to address global problems," European Commission President Jose Manuel Barroso said.

The leaders and their foreign ministers signed the treaty, in the bloc's 23 official languages, while a choir sang Beethoven's Ode to Joy in an ornate 16th-century riverside monastery.

British Prime Minister Gordon Brown, sharply criticized at home over his refusal to hold a referendum, skipped the televised ceremony and signed the treaty later at a private lunch with other leaders. He has insisted that treaty opt-outs he negotiated allow Britain to keep its sovereignty in key areas such as justice, home and foreign affairs, and security.

After lunch the delegations were to fly to Brussels, where a regular summit meeting is to be held Friday.

Environmentalists questioned the need for the two-hour Lisbon ceremony, which they say will leave a heavy carbon footprint and casts doubt on Europe's commitment to slowing down climate change.

To deflect criticism, some leaders are traveling together.

And Portugal has pledged to plant more than 1,000 trees to compensate for what it calculates is the 564 U.S. tons of CO2 related to the event.