The EU Council President Donald Tusk said the 26-page declaration, outlining how Britain will work with the bloc on trade, security, the environment and other issues, had been agreed "in principle" and would now be sent to the remaining 27 member states for approval.

Britain's embattled Prime Minister Theresa May hopes the declaration will convince sceptical lawmakers to approve her vision for the UK's departure from the bloc.

Officials said May will make a statement to parliament later in the day, presumably to sell the deal to MPs.

A special summit of all 28 EU leaders to sign the final Brexit deal is planned for Sunday, with May set to travel to Brussels the night before to finalise preparations.

First, the texts must be cleared by a meeting of top EU diplomats -- the summit's so-called "sherpas" -- on Friday.

The political declaration, seen by AFP, says future ties will be wide-ranging, covering economic cooperation, law enforcement and criminal justice, foreign policy, security and defence.

While the declaration has no legal weight, May will hope that ardent Brexiteers will be appeased by references to Britain developing "an independent trade policy" and spelling out an end to free movement of citizens between the EU and UK -- two of the key demands of the Leave campaign.

She has been under intense pressure from all sides over the withdrawal deal, with a slew of ministers resigning in protest and some of her own party MPs launching a bid -- stalled for now -- to unseat her.

Northern Ireland's Democratic Unionist Party (DUP), on whom May's Conservatives depend for their majority, has been flexing its muscles, fearing that efforts to avoid a hard border with Ireland will lead to the province drifting apart from the rest of the UK.

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"I have just sent to EU27 a draft Political Declaration on the Future Relationship between EU and UK," Tusk, who represents the 27 remaining EU member countries, tweeted.

"The Commission President (Jean-Claude Juncker) has informed me that it has been agreed at negotiators' level and agreed in principle at political level."