The guidelines come in response to British Prime Minister Theresa May formally starting Brexit negotiations on Wednesday, when she triggered Article 50.
Tusk's draft negotiating guidelines add that the other 27 countries are ready for a transitional deal after Britain's exit in 2019, but that any such arrangement must be under strict European Union rules.
But Tusk, who has sent the draft negotiating guidelines to member states, warned that the British government should respect some principles if it wants the talks to go well.
Key EU leaders such as German chancellor Angela Merkel, while sympathetic to Ireland's concerns, have to date been wary of the mandate highlighting specific national interests of any member states.
Tusk made these remarks at a joint press conference with Maltese Prime Minister Joseph Muscat in Valletta, capital of Malta, on the draft negotiation guidelines for Brexit.
Cameron's successor Mrs May on Wednesday notified the European Council president Donald Tusk that the United Kingdom was triggering article 50.
The draft proposals to be outlined by Mr Tusk are expected to include other crucial details, such as the sequencing of talks, in particular whether separation talks must be concluded before negotiators can move on to discuss Britain's future relationship with the EU.
Ukip leader Paul Nuttall said that Brussels' wish to "play hardball with the reciprocal rights of individual citizens" was not in the interest of member states, and that as Brexit neared they would see the EU's "rigid approach", not the United Kingdom, as the main problem. Meanwhile, Britain wants to control immigration into the country, possibly ending the rights of European Union members to live and work in Britain.
Fourth, we will seek flexible and creative solutions aiming at avoiding a hard border between Northern Ireland and Ireland.
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The announcement is the latest move in KFC's USA brand "turnaround", which it labels the "re-colonelization" of KFC. Its Chicken McNuggets are a top seller and the change put pressure on the rest of the industry to follow.
The official also said that only a summit of all remaining 27 European Union leaders can decide when there is enough progress on the withdrawal talks to start looking at a future relationship between Britain and the EU. Many EU officials believe it could be between two and five years.
"We want to talk about fairness and commitment", he said.
Meanwhile there was continued irritation over Mrs May's apparent attempts to link continued security co-operation with a new trade deal.
British foreign secretary Boris Johnson, in Brussels as North Atlantic Treaty Organisation ministers met U.S. secretary of state Rex Tillerson, said London was committed to European security and that it was "not some bargaining chip" in the Brexit talks.
Our partner are wise and decent partners.
"We will continue to play our part in ensuring that Europe remains strong and prosperous and able to lead in the world", she writes in the "Irish Times", a day after formally launching the process of the UK's exit from the EU.
The Brexit Secretary said: "This power will be time limited and Parliament will need to be satisfied that the procedures in the Bill for making and approving the secondary legislation are appropriate".
The EU's roadmap on Brexit negotiations leaves the United Kingdom and Spain to discuss what agreements will apply to Gibraltar, a British overseas territory on the edge of Spain that Spain has wanted back since it ceded it more than three centuries ago.