Mr Tusk’s letter — calling for a «phased» approach to Brexit — echoed German Chancellor Angela Merkel’s priorities, which she set out on Thursday.
«Before discussing our future, we must first sort out our past,» he said, listing three priorities:
On EU citizens living in the UK, he called for «effective, enforceable, non-discriminatory and comprehensive» guarantees
The UK must fulfil all its financial obligations agreed as an EU member state
A deal must be reached «to avoid a hard border between the Republic of Ireland and Northern Ireland»
«We will not discuss our future relations with the UK until we have achieved sufficient progress on the main issues relating to the UK’s withdrawal from the EU,» he said.
EU officials estimate that the UK faces a bill of €60bn (£51bn; $65bn) because of EU budget rules. UK politicians have said the government will not pay a sum of that size.
Reports say Irish Prime Minister (Taoiseach) Enda Kenny will also ask his EU partners to back the idea of Northern Ireland automatically joining the EU if the province’s people vote to unite with the Republic.