The EU has published its draft guidelines on the strategy for Brexit saying there needs to be "imagination" on how it answers the question of the Irish border.
European Council President Donald Tusk set out the EU's draft negotiating position, making clear Britain must settle its divorce from Europe before talks can start on trade relations.
On the question of the border between the Republic and Northern Ireland, Mr Tusk said: "We will seek flexible and creative solutions aiming at avoiding a hard border between Northern Ireland and Ireland. It is of crucial importance to support the peace process in Northern Ireland."
Avoiding a hard border... crucial to peace process in Northern Ireland.
Our duty is to minimise uncertainty, disruption caused by Brexit for citizens, businesses & Member States. It's about damage control.
Mr Tusk said: "Our duty is to minimise the uncertainty and disruption caused by the UK decision to withdraw from the EU for our citizens, businesses and Member States. As I have already said, in essence it is about damage control.
"We need to think of people first. Citizens from all over the EU live, work and study in the UK. And as long as the UK remains a member, their rights are fully protected. But we need to settle their status and situations after the withdrawal with reciprocal, enforceable and non-discriminatory guarantees.
"Second, we must prevent a legal vacuum for our companies that stems from the fact that after Brexit the EU laws will no longer apply to the UK.
"Third, we will also need to make sure that the UK honours all financial commitments and liabilities it has taken as a Member State. It is only fair towards all those people, communities, scientists, farmers and so on to whom we, all the 28, promised and owe this money. I can guarantee that the EU, on our part, will honour all our commitments.
The EU27 does not and will not pursue a punitive approach.
"Fourth, we will seek flexible and creative solutions aiming at avoiding a hard border between Northern Ireland and Ireland. It is of crucial importance to support the peace process in Northern Ireland.
"These four issues are all part of the first phase of our negotiations. Once, and only once we have achieved sufficient progress on the withdrawal, can we discuss the framework for our future relationship. Starting parallel talks on all issues at the same time, as suggested by some in the UK, will not happen.
"And when talking about our future relationship, we obviously share the UK's desire to establish a close partnership between us. Strong ties, reaching beyond the economy and including security cooperation, remain in our common interest.
"Let me conclude by saying that the talks which are about to start will be difficult, complex and sometimes even confrontational. There is no way around it. The EU27 does not and will not pursue a punitive approach.
"Brexit in itself is already punitive enough. After more than forty years of being united, we owe it to each other to do everything we can to make this divorce as smooth as possible.
"This is also why Prime Minister May and I have agreed to stay in close and regular contact throughout this process. I intend to visit Theresa May in London before the April European Council."