EU, UK agree Brexit talks principles: Barnier

"The most important thing I think now is for us to look to the horizon", said Britain's Foreign Secretary, Boris Johnson, ahead of a meeting with other foreign ministers in Luxembourg "Think about the future, and think about the new partnership, the deep and special partnership that we want to build with our friends".

Brexit talks have finally begun.

"We agreed on dates, organisation, and we agreed on priorities for the negotiations", Barnier said at a joint press conference with Davis.

The bloc insists on making "sufficient progress" on all three issues before discussing a future trade deal with the UK.

"Our objective is clear, we must first tackle uncertainties caused by Brexit", he told reporters.

Sabine Weyand, the EU's deputy chief negotiator, and Olly Robbins, the British prime minister's main adviser, will steer the discussions.

Mr Barnier made clear that Brussels intends to stick to its timetable of dealing with the terms of Britain's "orderly" withdrawal before moving on to discussing future trade relations.

"Business groups can help with the negotiations over trade, which is the model every other Government involved in trade negotiations operates, and we need to be brought in quickly to do this".

"Nothing is agreed until everything is agreed", he said, using a line also expressed by the EU.

Today's talks are likely to focus on the practical details of timings for the coming months, with the big, divisive issues left aside for now, officials said.

The UK kicked off talks in Brussels with both sides agreeing a schedule for dialogue as they attempt to pave the way to Brexit.

Issues surrounding trade are set to be addressed later. They will be tasked with exploring and testing options that will then be submitted to the top negotiators for their political blessings.

The issue dominated the opening day of Brexit negotiations between the United Kingdom and the European Union yesterday. "We must first tackle the uncertainties caused by Brexit, first for citizens but also for the beneficiaries of European Union policies and for the impact on borders, in particular Ireland".

When Britain leaves the European Union, the Irish border will become the EU's only land frontier with the UK.

"It has absolutely nothing to do with any negotiations inside the House of Commons", he insisted.

We also have to find solutions to maintaining all the commitments of the Good Friday Agreement.

Davis, who unlike May has long campaigned to leave the EU, will meet chief EU negotiator Michel Barnier, a former French minister, at the European Commission's Berlaymont headquarters at 11 a.m. "I am determined", Barnier said, quoting European Union founding father Jean Monnet in French. "We will work all the time with the UK, and never against the UK", Barnier said. A fair deal for both sides was possible, he said.

The difficulty, and potential acrimony, of the Brexit process could however be felt.

But the situation is very different from 12 months ago when the Brexiteers were riding high, with Prime Minister Theresa May's entire approach being called into question after a disastrous election performance on 8 June.

Davis stuck to May's script on Monday, saying without qualification that Britain would be leaving Europe's single market and its customs union.

Mr Lighthizer said: "As the United States' fifth largest export market, the United Kingdom is an invaluable trading partner".

European Union officials believe, however, that May and her ministers are coming round to accepting Brussels' rules.

Barnier said there will be one week of negotiations every month and the two sides will use the time in between to work out proposals.