British Prime Minister Theresa May says an agreement between Britain and the European Union guarantees the rights of 3 million EU citizens in the U.K. and 1 million Britons elsewhere in the bloc.
She also says it ensures there will be no hard border between Northern Ireland and the Republic of Ireland after Brexit.
She says Northern Ireland has "a set of unique circumstances" because it has the U.K.'s only land border with an EU country.
The border issue has been threatening to derail the divorce talks.
Earlier this week, Northern Ireland's DUP, the party that propped up May's government, scuttled a deal between the U.K and the bloc, prompting frantic diplomacy.
May said Friday (8 December) that the agreement would maintain an open border while preserving the constitutional and economic integrity of the U.K.
Earlier, European Commission President Jean-Claude Juncker lauded the breakthrough in Brexit talks and saids he will recommend that negotiations be broadened to future relations and trade.
Juncker told reporters Friday that "I believe that we have now made the breakthrough that we needed."
He said that he would recommend to European Union leaders that "sufficient progress has been achieved" on the terms of the divorce to start talking about issues like future relations and trade.
EU leaders meet in Brussels next Thursday and are likely to endorse the assessment that enough progress has been made on the terms of Britain's financial settlement, the status of Irish borders and the rights of citizens hit by Brexit.