European Union nations, now unfettered by Britain's decision to quit, achieved a 70-year-old ambition on Thursday to integrate their defences, launching a pact between 25 EU governments to fund, develop and deploy armed forces together.

European Council President Donald Tusk deemed the move "bad news for our enemies."

First blocked by the French parliament in the 1950s and later by Britain, which feared an EU army, the pact aims to end the squandering of billions of euros by splintered defence policies.

It is also aimed at lowering Europe's heavy reliance on the United States.

"More than half a century ago, an ambitious vision of the European Defence Community was created, but what was missing was the unity and courage to put it into practice," Tusk, who chairs EU summits, said of the failed 1950s attempt.

"The dream was at odds with reality. Today this dream becomes reality," he said in a speech in front of EU leaders and military personnel from each of the 25 countries involved.

EU foreign policy chief Federica Mogherini, who helped push through Franco-German plans for defence integration, said earlier it "turns the European Union into a credible security provider."

French President Emmanuel Macron, whose election victory in May gave new impetus to efforts to revive defence co-operation after Britons voted in 2016 to leave the bloc, hailed "concrete progress." Dutch Prime Minister Mark Rutte said the pact would make the EU more agile abroad and would support NATO, not replace it.

In one irony noted by EU diplomats, British Prime Minister Theresa May, who is attending the summit, sees the project championed by Britain in the late 1990s go on without the country due to Brexit. Denmark, which has an opt out from EU defence matters, and Malta, were the only other EU countries not signing up.

The pact, called Permanent Structured Cooperation, or PESCO, is meant as a show of unity and a tangible step in EU integration, diplomats said, particularly after Britain's decision to leave.

Trump criticism for lax defence spending

The concept of military integration was revived by France and Germany, with support from Italy and Spain, in a show of unity after Brexit.

It's sad that we needed Donald Trump to give us a boost, but whatever, it is the right outcome. - Joschka Fischer, former German foreign minister

A bigger impetus came from failings in the 1990s, when EU governments were unable to act in the Balkan wars and relied on U.S.-led NATO to stop the bloodshed on their doorstep.

In Libya in 2011, a Franco-British air campaign ran out of munitions and equipment and was again forced to turn to the United States, in what is considered an enduring embarrassment for the European Union, a major economic power.

Caught off guard by Russia's Crimea annexation in 2014 and facing threats ranging from state-sponsored computer hackers to militant attacks, EU governments appear to have overcome their aversion to working together in military matters.

U.S. President Donald Trump's criticism of low European defence spending, a host of divisions on foreign policy, and Trump's warnings to allies that they could no longer rely on the United States if they did not pay up have also played a role.

"It's sad that we needed Donald Trump to give us a boost, but whatever, it is the right outcome," said former German foreign minister Joschka Fischer, who as minister backed NATO's intervention in Kosovo in 1999 but opposed the 2003 Iraq war.

Qualified NATO support

Unlike past attempts at European defence integration, NATO backs the project, but NATO Secretary-General Jens Stoltenberg, who is attending part of the summit, urged against duplication.

Twenty-two EU countries are also members of NATO.

North Atlantic Treaty Organization (NATO) secretary general Jens Stoltenberg arrives at the European Council meeting on Thursday. NATO and the European Council pledge to coordinate efforts in the years ahead. (Stephanie Lecocq/EPA-EFE)

"There has to be coherence between the capability developments of NATO and the European Union. We cannot risk ending up with conflicting requirements from the EU and from NATO to the same nations," he told reporters "Forces and capabilities developed under EU initiatives also have to be available for NATO because we only have one set of forces."

Issues still remain about financing future EU missions. An EU defence fund, with money from the European Commission for the first time, still needs to be approved, although a pilot phase is already underway for defence research.

A 1998 Anglo-French EU defence accord is considered the genesis of Thursday's agreement. In a possible compromise on PESCO, Britain may be able to join in later on, but only on an exceptional basis if it provides funds and expertise.

Britain and France, both nuclear-armed, are Europe's two biggest military powers, and in 2010 set up a Combined Joint Expeditionary Force to cement long-standing ties in defence.

"We do face a number of threats across Europe," May said. "I'm very clear that although the British people took a sovereign decision to leave the EU, that does not mean that we were going to be leaving our responsibilities in terms of European security," she told reporters.