BRUSSELS -- The European Union cleared the way Friday for Brexit talks with Britain to move onto the second stage but it warned that the discussions on trade and other matters relating to their future relationship will be "dramatically difficult."
The 27 leaders authorized the move with little fanfare on Friday, almost nine months after Britain triggered the two-year mechanism by which it will leave the bloc. With so little time left before Brexit is due to take place, negotiators face a tight deadline to carve out a wide-ranging separation deal.
EU Council President Tusk said a deal by March 2019 is "still realistic and of course dramatically difficult. For sure, the second phase will be more demanding, more challenging than the first phase."
EU Commission President Jean-Claude Juncker said he expected talks to resume in March, giving negotiators little over eight months to wrap up the deal, since the EU legislature and the EU member states will need time to get the necessary approvals in time for the scheduled Brexit day on March 29, 2019.
To give Britain more time, a transition phase of about two years is expected to be an early point of discussion.
May was already back in Britain on Friday when the 27 other EU leaders agreed that "sufficient progress" had been made in the initial Brexit talks on the outstanding EU bill Britain will have to pay, the rights of citizens in each other's areas and the commitment to maintain a transparent border between Ireland and Northern Ireland.
She said their agreement "is an important step on the road to delivering a smooth and orderly Brexit and forging our deep and special future partnership."
Since March, the EU side has been marked by a high degree of cohesion, which contrasts with the sometime-chaotic nature of Britain's approach. The coming talks could well test that cohesion in the EU, not least because of the divergent trading relationships the 27 remaining EU countries have with Britain.
Friday's clearance provides a welcome boost to May, who earlier this week lost a key parliamentary vote over giving lawmakers the final say on the Brexit deal.
May received a round of applause from EU leaders Thursday night after giving her assessment of progress in the talks.
European Commission President Jean-Claude Juncker said Friday that "some of us thought, including me, that she did make big efforts and this has to be recognized."
May's first priority in the next phase of talks is to establish a transition period, likely involving Britain remaining part of the single market and the customs union and probably lasting about two years. A transition period would ease Britain out of the EU and provide some certainty to business. Many British firms, particularly in the finance sector, have warned that they might put contingency plans in place soon that could involve them relocating activities into the EU.
During any transition, the EU is demanding that London should give up its seat at the leaders' table, lose all its lawmakers in the European Parliament and remove its judges from Europe's courts. However, it would still have to obey EU laws and respect the primacy of the European Court of Justice.
While sympathizing with May, leaders said they wanted the British prime minister to provide more details on what she is looking for both in the transition period and in the future relationship.
"We need a little bit more clarity from the U.K.; what type of relationship we shall be entering into," said Croatian Prime Minister Andrej Plenkovic.
And Irish Prime Minister Leo Varadkar said "lot of thinking" needs to be done about future relations.
"There has been a lot of divergent thinking on what that should look like," he told reporters.
Varadkar held separate talks with May overnight "to compare notes," and he said they would meet again early in the new year.
When asked about the chances that Britain might not leave in 2019 as planned, most leaders said only that this should be up to the British people and parliament.