Britain voted by a 52 to 48 percent majority to leave the European Union - the first member state ever to do so.
Opposition Labour leader Jeremy Corbyn said his party accepted the Prime Minister had a mandate to start the process of leaving the EU.
"Everything is ready on this side", Margaritis Schinas, the spokesman for European Commission chief Jean-Claude Juncker, told a briefing.
Theresa May has finally revealed that she will trigger Article 50 on March 29, launching the two-year countdown to Brexit.
May has already announced that she will make a statement to the House of Commons shortly after invoking Article 50 of the Lisbon Treaty.
Britain's Parliament last week gave its final approval to May's Brexit plans, and the prime minister had at one point been expected to trigger Article 50 then. The government is clear in its aims: "a deal that works for every nation and region of the United Kingdom and indeed for all of Europe, a new, positive partnership between the United Kingdom and our friends and allies in the European Union". European leaders have drawn a tough line, signaling they will not allow Britain to enjoy the benefits of EU membership but not bear the responsibilities. The Government will want due recognition of Ireland's priorities in the initial negotiating position.
March 29-31 - Within 48 hours, Tusk sends to the 27 other member states his draft negotiating guidelines.
If Scotland votes for independence, expect more years to negotiate its split from London and possible re-entry to the EU.
It is not quite accurate to say nothing much is going to happen after article 50 is triggered next week, but the huge excitement built up around "the date" is likely to prove misplaced.
Another crucial point will be how Britain approaches the idea of a transitional deal to cover the period after it leaves the European Union, but before a new trade deal is negotiated.
May and European Union leaders say transitional arrangements may well be needed, to give more time to agree a future trade deal and give people and businesses time to adjust to the divorce.
London has repeatedly said it wants to maintain good relations with its European allies, but major battles await, in particular over budget contributions, immigration and future trade ties.
"For nine months since the European Union referendum, there has been no attempt by the United Kingdom government to seek a meaningful discussion or agreement with the devolved administrations".
She will visit Wales with Brexit Secretary David Davis and Welsh Secretary Alun Cairns, and will meet First Minister Carwyn Jones as well as business leaders. Leaving the Single Market was not on the ballot paper in the referendum, it is a political choice made by Theresa May. Mrs May is not attending the event.