LONDON (Reuters) - Prime Minister Theresa May needs to speed up negotiations with the European Union, business leaders told her on Monday, amid concern Britain will crash out the world’s biggest trading bloc without a deal.

Business leaders including Germany's BDI Managing Director Joachim Lang and Carolyn Julie Fairbairn director-general of the Confederation of British Industry pose for a group picture outside 10 Downing Street, London, November 13, 2017. REUTERS/Peter Nicholls

Slow progress in the talks with the European Union has unsettled businesses and drawn warnings that unless a transition is agreed soon, some may begin activating Brexit contingency plans - which may include moving out of Britain.

May had invited 15 business groups from Britain and continental Europe for talks in her Downing Street office to urge them to back her Brexit strategy and persuade companies not to move overseas.

The executives told May she needed to provide more clarity on three issues critical for talks to progress: negotiating any potential exit bill, settling the rights of EU citizens living in Britain, and arrangements for the border in Ireland.

“Business is extremely concerned with the slow pace of negotiations and the lack of progress,” said Emma Marcegaglia, president of BusinessEurope, a lobby group that speaks for companies in European countries, including Britain.

May wants to agree with the EU the broad outline of a so-called implementation period of around two years after Britain’s exit from the EU in March 2019. During that period, its access to the EU single market would remain largely unchanged while new arrangements were put in place.

International companies have become increasingly vocal in recent weeks over fears that Britain will leave the EU without a trade deal, a move that would send shockwaves through global markets and fracture some supply chains.

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Carolyn Fairbairn, director general of the Confederation of British Industry, said all the businesses at the meeting warned May about the damage leaving without a trade deal could do.

“We now need to move beyond warm words if jobs, investment and living standards are to be protected,” she said.

Talks between Britain and the EU are currently deadlocked.

The European Union told Britain last week to spell out what it will pay Brussels when it leaves the bloc in 2019 or face more delay in talks on future trade ties that are vital for business.

Progress at a Brussels summit next month is seen as an important milestone in the talks as businesses seek clarity by the new year when many will take investment decisions dependent on conditions after Brexit.

May has stepped up her engagement with businesses in recent months, regularly meeting with British lobby groups and senior executives, but they say the government has offered little detail about what a future trade deal will actually look like.

Monday’s meeting was the first time she expanded that programme to include representatives from industry groups from Germany, France, Italy, Spain and other member states as well as EU-wide organisations.

They also met business minister Greg Clark, Brexit minister David Davis and the junior Treasury minister Stephen Barclay.

Danny McCoy, chief executive of the Irish Business and Employers Confederation, told national broadcaster RTE that Davis had outlined plans for a free-trade agreement that involved no tariffs and no regulatory barriers.

“That was one of the more concrete things to come out from the discussion,” he said. “For business, I would be more confident today than I was a week ago that we can avoid a hard Brexit.”