Tusk said he has spoken to all 27 European Union leaders and each one told him their priorities regarding Brexit are "protecting the peace process and avoiding the hard border".
The EU has repeatedly called on Britain to lay out its position on a trade deal after it leaves the union in March 2019, and Tusk recently said he would publish the guidelines whether Britain was ready or not.
British Foreign Secretary Boris Johnson said on Thursday (March 8) that a so-called hard Brexit should not hold any "terrors" and Britain would do "very well" operating under World Trade Organisation rules after leaving the EU.
Britain's Secretary of State for Exiting the European Union David Davis arrives In Downing Street in London Thomson Reuters LONDON (Reuters) - Parliament will not be able thwart Brexit by using a vote expected later this year on the final deal negotiated with the European Union to overturn the result of the 2016 referendum, Brexit minister David Davis said on Tuesday.
"Any backsliding on commitment made so far would create a risk to further progress in Brexit negotiations", EU President Donald Tusk told reporters in Dublin.
He said destabilising the peace process in Northern Ireland "must be avoided at all costs" and that it is up to the United Kingdom to put forward a "specific and realistic plan" to avoid a hard border.More news: Jupiter is full of mysteries: NASA looked inside the planet
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In the FTA we can offer trade in goods, with the aim of covering all sectors, subject to zero tariffs and no quantitative restrictions. The hope is that that meeting will produce an outline agreement on a transition deal which will see current rules and regulations stay as they are until at least December 2020. Instead, he said it was time to "address the sceptics who say a trade deal including financial services can not be done because it has never been done before".
The EP will not play a role in the UK-EU talks. To do so is an insult to the people of Northern Ireland, who have worked so hard to bring peace to our country.
Hammond said Brussels had originally aimed to include financial services in a free trade deal with Canada which in the end failed to provide much new market access for banks.
"We should all be clear that, also when it comes to financial services, life will be different after Brexit".
Last December the Bank of England proposed allowing European Union banks in Britain to continue as branches in London after Brexit on condition of some form of reciprocity from Brussels to avoid lenders having to find extra capital to become fully fledged subsidiaries.