The European Union wants Northern Ireland to have a different Brexit deal to the rest of the UK, papers seen by the BBC suggest.
The document says the UK should take responsibility for finding a “unique solution” so people can work, go to school or get medical treatment either side of the Irish border.
Details will be published by the EU’s chief negotiator Michel Barnier later.
He has said “a lot more substantial work” is needed on the border issue.
The EU’s position paper comes as MPs prepare to debate the EU Withdrawal Bill in Parliament. The legislation will convert all existing EU laws into domestic ones ahead of Brexit – due to take effect at the end of March 2019.
Ministers said passing the legislation would form an “essential foundation” for post-Brexit Britain, but Labour has vowed to vote against it as it stands, calling it a power grab by the government.
- All you need to know about Brexit
- MPs to begin debate on key Brexit bill
- EU warning over Irish border post-Brexit
- What will the deal do to the 310-mile border?
The EU will release a series of position papers later as the debate in the House of Commons gets under way.
Plans to protect Irish cross-border co-operation in areas like health, education, transport and fishing will feature, as well as proposals around issues such as data protection, intellectual property and customs arrangements.
Ireland’s place in the EU’s single market or customs union is also mentioned in the document.
It says nothing can affect the country’s membership even though the UK government has already said it would leave the customs union.
But, the EU has also reminded Britain that negotiations can only move on when it rules “sufficient progress” has been made on issues of citizens’ rights and the UK’s financial obligations.
The UK government released its own position paper on Northern Ireland last month.
It called for an “unprecedented solution” for the border and stressed there should be no physical infrastructure – such as customs posts – anywhere along it.
But critics said the proposals lack credible detail, with Labour deriding the plans as “a fantasy frontier”.