Theresa May has written a letter to the British public pleading for their support for her Brexit deal, as the EU prepares to formally sign it off.
The prime minister said her agreement promises a "brighter future" for the UK and leaving the EU next year will be "a moment of renewal and reconciliation for our whole country".
EU leaders are in Brussels for a summit to decide whether to endorse the deal.
European Council chief Donald Tusk has recommended all countries approve it.
Spain - which had threatened to boycott the summit - will attend after a last-minute disagreement over Gibraltar was resolved on Saturday.
However, even if the EU agrees to the deal, it needs to be passed by UK Parliament, and many MPs - including in Mrs May's own Conservative Party - have stated they will vote against it.
In May's "letter to the nation" - published on the eve of the EU summit where she hopes the 27 other EU countries will back her deal - the PM claims the deal is "in our national interest" and works for all parts of the UK.
Leaving the EU on 29 March 2019 will mark "a new chapter in our national life," she said.
"It must mark the point when we put aside the labels of 'Leave' and 'Remain' for good and we come together again as one people.
"To do that we need to get on with Brexit now by getting behind this deal."
The prime minister said she would be campaigning "with [her] heart and soul" to get MPs to pass the deal in the House of Commons and "honour the result of the referendum".
She said the deal delivers on Brexit by ending free movement of people and "vast" annual payments to the EU.
"With Brexit settled", the government will be able to focus on issues such as the economy, the NHS and building homes, she added.
What will happen at the summit?
On Sunday morning, EU leaders will be asked to approve two key Brexit documents:
- The political declaration, which sets out what the UK and EU's relationship may be like after Brexit - outlining how things like UK-EU trade and security will work.
- The EU withdrawal agreement: a 585-page, legally binding document setting out the terms of the UK's exit from the EU. It covers the UK's £39bn "divorce bill", citizens' rights and the Northern Ireland "backstop" - a way to keep the border with the Republic of Ireland open, if trade talks stall.
There is no formal vote on Sunday but the EU expects to proceed after reaching a consensus, with the agreement likely to be approved.
What happens afterwards?
If the EU signs off the withdrawal deal, Mrs May will then need to persuade MPs in the UK Parliament to back it.
A vote is expected in December. Labour, the Liberal Democrats, the SNP and the DUP have all said they will vote against the government's deal, as well as many Conservatives.
The agreement will also have to go back to the European Council, where a majority of countries (20 out of 27 states) will need to vote for it. It will also need to be ratified by the European Parliament.
If MPs reject the deal, a number of things could happen - including leaving with no deal, an attempt to renegotiate or a general election.
Chancellor Philip Hammond is working with other Cabinet ministers to trying to persuade Mrs May to opt for a softer Brexit deal, which they believe could get through Parliament if her original deal is rejected.
reported several senior ministers are working on a plan B - for a Norway-style relationship with the EU.
What May's critics are saying
Labour MP Ian Murray called the 800-word letter an "utter work of fiction" and described Mrs May as "desperate".
He repeated the words of Labour leader Jeremy Corbyn, who has previously called the agreement "the worst of both worlds".
And Welsh Labour MP Stephen Doughty responded with his own letter, saying he was "not buying it".
Among the Conservatives, Tory MP Sarah Wollaston called for a further referendum on the deal, and said: "Not a brighter future, just dimmer and diminished".
Meanwhile, writing in
leading Tory Brexiteer Jacob Rees-Mogg - who has previously called for Mrs May to be replaced as party leader - claimed the deal "does not deliver on Brexit".
Former Foreign Secretary Boris Johnson, speaking at Northern Ireland's Democratic Unionist Party conference on Saturday, said the UK was on the verge of "making a historic mistake" and
Why was Spain unhappy?
Spain threatened to not show up over concerns about its role in future trade arrangements involving Gibraltar - a British Overseas Territory with 30,000 residents.
But it dropped its threat after saying it had received assurances from the UK.
The Spanish PM Pedro Sanchez claimed the UK and EU had agreed to its demands but BBC Europe correspondent Kevin Connolly said UK assurances did not contain anything substantially different from the withdrawal agreement.
He said there was a suspicion that Spanish ministers were "showboating a little for the domestic electorate" on the eve of elections in the south of Spain.