LONDON (Reuters) - The British government will publish detailed plans for its future relationship with the European Union next month in an attempt to break the deadlock in Brexit negotiations.

Britain's Prime Minister Theresa May leaves 10 Downing Street, in London, May 8, 2018. REUTERS/Hannah McKay

A so-called White Paper is likely to outline proposals for future customs arrangement and for specific sectors including financial services, agriculture and cars, according to two government officials.

The document, expected to extend to more than 100 pages, will be published before a summit of EU leaders on June 28-29, they said.

It will follow repeated complaints from EU officials that Britain has not been clear on what it wants. Prime Minister Theresa May is struggling to overcome deep divisions in her government over the nature of Britain’s divorce with the EU and find agreement on a customs proposal to take to Brexit talks in Brussels, which have all but stalled in recent weeks.

Brexit minister David Davis told his cabinet colleagues on Tuesday that the document will be the most significant publication on relations with the EU since the 2016 referendum when Britons voted to leave the bloc, officials said.

It is “an opportunity to set out clearly to both a domestic and an EU audience the reasoning behind our approach”, Davis said. The document will “include detailed, ambitious and precise explanations of our positions...it should set out what will change and what will feel different outside the EU”.

May’s decision to leave the EU’s customs union, which sets tariffs for goods imported into the bloc, has become one of the main flashpoints in the Brexit debate and she is struggling to build a consensus around one of two customs options.

Her Brexit cabinet committee failed again on Tuesday to decide a customs plan, but ministers did agree that big decisions had to be taken soon, one official said.

Publication of the document may help to appease business leaders who have complained that almost two years after the referendum they have little idea about what Britain’s negotiating priorities are for their sectors.

White papers are policy documents produced by the government that set out proposals for future legislation.

The document may also outline positions on future dispute settlement, cooperation with EU bodies, the security partnership, law enforcement and defence and foreign policy.

Diplomats and officials in Brussels have raised doubts about whether the bloc and London will be able to mark a milestone in the negotiations at the EU summit.

The current schedule sets progress for the talks in June as an important step towards a final Brexit deal in October, leaving enough time for an elaborate EU ratification process before Britain is expected to leave the bloc in March next year, the officials said.

Although May set out in March the broad aims of Britain’s plan for a future relationship between Britain and the EU, a number of questions remain, including how far different sectors of the economy will diverge from the bloc’s rules.