EU leaders will consider allowing the United Kingdom to remain in the European Union for another year; with the option of leaving earlier if a deal is ratified.
Britain's Prime Minister Theresa May has met key EU leaders, ahead of an emergency summit in Brussels on Wednesday.
May held talks with French President Emmanuel Macron, and Germany's Angela Merkel - hoping to convince the two to back her request to delay Brexit until June 30.
Without the approval of the bloc, the UK will crash out on Friday.
Al Jazeera's Rory Challands reports from London.