With just six months to go until the United Kingdom is due to leave the European Union, negotiations are at what Prime Minister Theresa May has called an impasse.
If she can clinch a deal with the EU, she will still have to sell it to her divided Conservative Party and win parliamentary approval. If she cannot, the United Kingdom could face leaving without a deal, a national election or even another referendum.
Below are significant dates as Britain nears its departure from the EU in March:
LABOUR PARTY CONFERENCE - September 23 to 26
Britain's opposition Labour Party will vote against any deal May clinches with the European Union and is open to a second referendum with the option of staying in the bloc, Brexit spokesman Keir Starmer said on Tuesday.
CONSERVATIVE PARTY CONFERENCE - September 30 to October 3
The Conservative Party often holds its annual conferences in a febrile atmosphere. Last year, May gave a calamitous speech in which she lost her voice, was handed a resignation notice by a prankster, and the stage backdrop fell apart as she spoke.
This time tensions over her Brexit plan are likely to dominate and rivals, such as former foreign minister Boris Johnson, are likely to use the occasion to make their leadership pitch to grassroots members.
Although May will be keen to focus on domestic policy rather than Brexit, the conference will allow her to sound out support for whatever agreement she is hoping to reach with the EU.
EUROPEAN COUNCIL - October 18
May meets fellow EU leaders and the European Commission to try to seal deals on the terms of Britain's withdrawal and what kind of relationship it has in the future.
Top EU officials have said the meeting will be "the moment of truth" in the negotiations and they will gauge whether talks have advanced enough to formalise a Brexit deal in November.
The agreement will have to cover trade and how to prevent a return of border controls on the frontier between Northern Ireland and the Irish Republic, which will become Britain's only land border with the EU. These are the main areas of disagreement which have caused May's government to step up preparations for leaving without any deal.
Both sides have said that talks could slip into November without endangering the overall timeline.
SPECIAL BREXIT SUMMIT - weekend of November 17-18
EU leaders agreed in Salzburg in mid-September to hold a special summit on the weekend of November 17-18 to seal a Brexit deal with Britain if it is done.
EU COUNCIL - December 13-14
European Union leaders are due at an EU Council meeting on December 13-14. If a deal is not struck in November, this summit could be one of the last chances for a deal if parliaments on both sides are to ratify the deal by exit day in March.
UK PARLIAMENTARY VOTE ON BREXIT DEAL - Unscheduled
If May secures a deal, she has to get parliament to approve it. She would need about 320 votes in parliament to get approval.
Her Conservatives hold 316 seats in the 650-seat lower house, and she relies on a Northern Irish party to win parliamentary votes.
Labour has indicated it would vote against her deal so unless she can win over her own lawmakers, she could lose a vote in parliament.
Failure could trigger a move against her leadership of the Conservative Party, or the government's collapse and an early election.
EUROPEAN PARLIAMENT RATIFICATION - Unscheduled
The European Parliament must also sign off on any agreement reached between May and the other 27 EU leaders. If the legislative starts dealing with it in November or even December, it should still be able to complete its elaborate ratification process in time for Brexit day.
It could hold a final plenary vote during a plenary session set for March 11-14. But it would be getting busy then with campaigning ahead of European elections next May - in which Britain would no longer take part.
EU officials have suggested a further delay may still be possible if negotiators are very close to sealing a deal. But it would just be a few extra weeks at best, as the current EU parliament holds its last plenary session on April 15-18, 2019. That is already beyond the current Brexit date.
NO DEAL STATEMENT
If there is no deal by January 21, 2019, the British government must make a statement within five days on what the United Kingdom plans to do, according to the European Union (Withdrawal) Act of 2018.
May said this week a 'no-deal' Brexit would be better than the EU's standing offer.
BREXIT - March 29, 2019 at 2300 GMT.
Britain will formally leave the EU. Providing an exit deal is agreed, there will be a transition period during which the bulk of the bloc's rules and regulations continue to apply while the British government formulates and implements replacement policies on issues such as immigration.
TRANSITION PERIOD ENDS - December 31, 2020
The transition period, designed to ease the impact on businesses and relieve uncertainty, is due to end. Little has been agreed so far about the new arrangements between Britain and the EU on trade, customs and other major issues.