The European leaders on Sunday endorsed the Brexit deal at the European Union (EU) summit, a major breakthrough since the lengthy Britain-EU Brexit negotiation started one and half years ago.
The European Council agreed on the withdrawal of the United Kingdom of Great Britain and Northern Ireland (UK) from the European Union (EU) and the European Atomic Energy Community.
The political document covers Britain's 39-billion-pound "divorce bill", citizens' rights and the Northern Ireland "backstop" - a way to keep the Irish border open, if trade talks stall.
The European Council also approved the Political Declaration setting out the framework for the future relationship between the EU and Britain.
The Political Declaration sets out what Britain and the EU's relationship may be like after Brexit, outlining how things like UK-EU trade and security will work.
European Commission President Jean-Claude Juncker said that "it's a sad day," as he arrived Sunday for an EU summit in Brussels to endorse the Brexit agreement. He told reporters that the summit "is neither a time of jubilation nor of celebration. It's a sad moment, and it's a tragedy."
"Let's pave the way towards a close post-Brexit relationship," he said. "The UK is leaving the European Union not Europe."
Asked whether a better agreement can be found, should the British Parliament reject it, Juncker said: "This is the deal. It's the best deal possible. The European Union will not change its fundamental position."
Britain is scheduled to leave the economic and political union on March 29, 2019.
The terms of the UK's withdrawal have been under negotiation since June 2016 following a referendum, in which 52 percent voted for Brexit.
Even if the EU approves the deal, it still has to be passed by the British Parliament as many MPs have stated their opposition.