British Prime Minister Theresa May has said the Brexit deal announced in Brussels ensures there will be "no hard border" between Ireland and the UK.
Here are Mrs May's "six commitments to Northern Ireland".
"Today I agreed a joint report between the Government of the United Kingdom of Great Britain and Northern Ireland and the European Union on the progress of our negotiations.
"This covered the rights of EU citizens living in the UK and UK citizens in the EU; our financial settlement with the EU; and ruling out a hard border between Northern Ireland and Ireland.
"This progress now enables the UK government to move to the next phase of negotiations. This next phase will focus on securing the deep and special partnership between the United Kingdom and European Union that we all want to see.
"As a Prime Minister who hugely values Northern Ireland's position within our United Kingdom - and believes passionately that the United Kingdom is stronger and better together - I want to set out six key commitments to Northern Ireland, principles that have guided me in the negotiations with the EU.
"These commitments are consistent with our steadfast support for the Belfast Agreement and its successors; the principles that underpin them; the institutions they establish; and, the rights and opportunities they guarantee for everyone.
"This government will continue to govern in the interests of the whole community in Northern Ireland and uphold the Agreements that have underpinned the huge progress that has been made over the past two decades.
"First, we will always uphold and support Northern Ireland's status as an integral part of the United Kingdom, consistent with the principle of consent.
"The government I lead will never be neutral when it comes to expressing our support for the Union.
"Second, we will fully protect and maintain Northern Ireland's position within the single market of the United Kingdom. This is by far the most important market for Northern Ireland's goods and services and you will continue to have full and unfettered access to it.
"Third, there will be no new borders within the United Kingdom of Great Britain and Northern Ireland. In addition to no hard border between Northern Ireland and Ireland, we will maintain the Common Travel Area throughout these islands.
"Fourth, the whole of the United Kingdom, including Northern Ireland, will leave the EU customs union and the EU single market. Nothing in the agreement I have reached alters that fundamental fact.
"Fifth, we will uphold the commitments and safeguards set out in the Belfast Agreement regarding North-South Co-operation. This will continue to require cross-community support.
"Sixth, the whole of the United Kingdom, including Northern Ireland, will no longer be subject to the jurisdiction of the European Court of Justice.
"These negotiations are crucial for the future of Northern Ireland and the whole United Kingdom. Whether you voted Leave or Remain, I am determined to deliver an outcome that works in the best interests of everyone across the United Kingdom."