The U.K. is one of only a handful of EU states capable of providing battlegroup headquarters | Pool photo by Paul Grover/Getty Images Britain pulls out of EU defense force UK insists the move does not undermine commitment to Continent’s security.

LONDON — The U.K. has withdrawn its offer to lead a battle-ready EU military force after Brexit, the first concrete example of the impact of the country's EU exit on European defense cooperation.

In a letter obtained by POLITICO, the U.K. informed the chairman of the EU military committee last Wednesday that it would no longer be the lead nation in a 1,500-strong “battlegroup” for EU defense in 2019 because of ongoing uncertainty over Britain’s withdrawal from the European Union.

Britain’s decision comes despite Prime Minister Theresa May’s insistence that the U.K.’s commitment to European security is “unconditional.” The timing of the announcement has the potential to embarrass the U.K. government in the wake of Russia’s alleged use of chemical weapons in Salisbury and Britain’s subsequent diplomatic push to secure the support of its allies in Europe and the U.S.

After initial equivocation, France, Germany and the United States rowed in behind the U.K., accusing Moscow of being culpable for the nerve agent attack in Salisbury, which has left a Russian double agent, his daughter and a British policeman fighting for their lives.

“... the offer of a battlegroup in the period immediately following our exit strikes us an unnecessary complication" — Britain’s Lieutenant General George Norton

A number of EU military powers take it in turns to provide the bulk of the troops for the so-called EU battlegroup, a force established as part of a broader push to give the EU more military clout.

No battlegroup has yet deployed to a crisis zone, but they are ready if called upon. Britain was due to take over responsibility for providing the battle-ready force in the second six months of 2019, during the Brexit transition period.

The U.K.’s decision to withdraw from the roster of EU countries offering to lead battlegroups is likely to spark concern on the Continent that London’s commitment to European security is now also uncertain, despite May’s repeated reassurance that this is not the case.

'Clarity of purpose'

In the letter informing Brussels of the U.K.’s decision, Britain’s Lieutenant General George Norton said the decision to withdraw from the program was because of the logistical problems caused by Brexit, and insisted Britain could still remain part of the program further down the line if a political agreement could be struck.

Writing to General Mikhail Kostarakos, chairman of the EU military committee, Norton said the U.K. is prepared to offer a battlegroup for the EU rota in future once the Brexit uncertainty had been cleared. He added the U.K.’s offer had always been “provisional.”

Norton said that while Britain’s withdrawal had been under discussion since September last year, it was important to clarify the decision to give the EU time to prepare.

France, Italy, Germany and Greece are the only other countries with national headquarters having sufficient capacity to command a European operation.

“Military activities, however, require clarity of purpose, and planning; not least of which involves the time that is necessary to force generate credible capabilities," the letter states. "The U.K. believes that, for the practical purposes of the time needed for the EU and member states to identify and assign a stand-by battlegroup for the second half of 2019, a decision should not be delayed. Consequently we formally withdraw our provisional offer of a battlegroup for the period 2019-20.”

The letter goes on: “Our prime minister’s unconditional commitment to European security of course stands, but the offer of a battlegroup in the period immediately following our exit strikes us an unnecessary complication."

Britain’s defense ministry did not respond to a request for comment before this article was published.

Any decision to deploy the battlegroup would be made by EU leaders at the European Council, which Britain will leave in March 2019. However, all lead battlegroup countries retain a veto over deployment.

The U.K. is one of only a handful of EU countries capable of providing battlegroup headquarters.

Britain also currently leads the EU’s counter-piracy mission “Atlanta” off the coast of Somalia, commanding the operation out of Northwood military headquarters in Hertfordshire.

France, Italy, Germany and Greece are the only other countries with national headquarters having sufficient capacity to command a European operation. The U.K., for example, is providing the headquarters for a Dutch/Belgian battlegroup in 2018.

London also plays an important role in Operation Sophia — the counter-smuggling operation in the Mediterranean that is commanded from Italian national headquarters — as well as stationing troops in Estonia to act as a deterrent to any military action by Russia.

Whether Britain continues its involvement in the EU battlegroup program after Brexit will depend on whether the U.K. can negotiate more involvement in decision-making and control of missions than is normally offered to third countries, U.K. officials said. If this proves impossible, officials say it is unlikely Britain will continue to take part in EU missions in the future.