Formally notifying Tusk of Britain's intention to leave the bloc, by triggering Article 50 of the EU's Lisbon Treaty, sets the clock ticking on a two-year negotiating period to end the UK's 44 years of membership.
But that concession to Theresa May two days after she triggered a two-year countdown to withdrawal was accompanied by elements in the draft circulated by European Union summit chair Donald Tusk that the British prime minister may find less palatable.
Tusk said: "Our duty is to minimise uncertainty and disruption caused by the UK's decision to withdraw from the European Union".
The EU has outlined its strategy for Brexit negotiations, suggesting talks on a trade deal could begin once "sufficient progress" is made on a separation settlement with the UK.
According to Article 50 of the Lisbon Treaty-which launched the official divorce papers between the United Kingdom and the EU-Britain must legally separate within the next two years.
Another issue is securing the rights of both millions of mainly East European EU citizens in Britain and British people living in other member states.
The priority of the EU's remaining 27 member states would be to protect their social and economic interests, Sigmar Gabriel told German parliament, a day after British Prime Minister Theresa May launched the two-year negotiation process to quit the bloc.
He added that "the EU-27 does not and will not pursue a punitive approach" because "Brexit in itself is already punitive enough".
Workers rights, environmental protection and consumer rights now enshrined in European Union laws would continue as before when Britain left, he added.
The EU has asked for a payment worth £50 billion ($62.36 billion) but Prime Minister Theresa May and Brexit minister David Davis are keen to hand over a significantly reduced sum.
Within hours of the result on June 23 past year, in which 17.4 million people vote Leave in a 52 per cent to 48 per cent victory for Brexit campaigners, Mr Cameron resigned.
By converting the body of European Union law into British legislation, May's government hopes to ease those concerns by offering that "wherever practical, the same rules and laws will apply after exit day".
And when it comes to the U.K.'s land border in Ireland, which is key to the Northern Ireland peace process, Tusk's draft guideline says that "flexible and imaginative solutions will be required". The EU put emphasis on providing clarity to European citizens, businesses, stakeholders and global partners early in the negotiations.
Only once we have achieved sufficient progress on the withdrawal, can we discuss framework for the future.
"This is an important point in the future negotiations of the United Kingdom's exit from the European Union", said Spanish minister Inigo Mendez de Vigo.
Government sources familiar with discussions with Mr Tusk's office say they expect the guidelines will be "quite short and terse", and will concentrate on broad principles and objectives rather than detailed outcomes.
"Brexit has made us, the community of 27, more determined and more united than before", he wrote.