“Obviously we will stand up for our interests as Britain too will stand up for its interests,” Ms. Merkel told a news conference after the summit meeting. “We’re trying to forge a strong European Union of 27. This is the sort of spirit with which we approach these negotiations.”.

The adoption of the guidelines was followed by “a general round of applause,” Ms. Merkel noted.

One of the thorniest issues is getting Britain to guarantee that the three million citizens of other European Union nations who are living in Britain and the 1.2 million Britons living in the European Union can maintain their residency rights and other entitlements.

Safeguarding citizens’ rights was “priority No. 1,” Donald Tusk, the president of the European Council, the body that represents the bloc’s leaders, told a news conference after the meeting. “Today’s discussion made clear that when it comes to reaching a decision on citizens’ rights not only speed is of the essence but above all quality, as so many people’s lives depend on it,” he said.

The leaders also called on Britain to meets its outstanding financial obligations so that other member states can avoid paying higher costs after the British withdrawal. The outstanding bill could amount to as much as 60 billion euros, about $65 billion. But British citizens and politicians are balking at paying such a large sum.

Another key issue: pushing Britain to maintain a free flow of trade and people between Northern Ireland, which will leave the bloc with Britain, and the Republic of Ireland, which will remain a full member of the European Union.