The Prime Minister has written a 'letter to the nation', insisting her EU withdrawal agreement will work "for our whole country and all of our people, whether you voted 'Leave' or 'Remain'".
Theresa May said the deal will "honour the result of the referendum", taking back control of UK borders, money and laws, and taking the country out of EU programmes like the Common Agricultural Policy and Common Fisheries Policy "that do not work in our interest".
She said the deal "works for every part of our country - for England, Scotland, Wales and Northern Ireland, for our Overseas Territories like Gibraltar, and also for the Crown Dependencies".
And she called for Brexit day on March 29 next year "to be a moment of renewal and reconciliation for our whole country ... when we put aside the labels of 'Leave' and 'Remain' for good and we come together again as one people".
EU leaders gathered in Brussels this morning endorsed the terms of the Withdrawal Agreement and the Political Declaration finally agreed with the commission last week.
However European Commission president Jean-Claude Juncker has warned Britain cannot expect to get a better Brexit deal if Parliament rejects the agreement hammered out by Theresa May.
Dutch Prime Minister Mark Rutte said he was "absolutely confident that Theresa May has everything now on the table to argue for a majority in the British parliament".
Speaking to reporters as he arrived at the Europa building of the European Council, he added: "I don't want to contemplate the no-vote, I think there will be a yes vote. But more in general, I think this is the max we can all do. Both Theresa May and her government, as well as the European Union.
"(There are) no victors here today, nobody winning. We are all losing. But given that context this is acceptable."
EU chief negotiator Michel Barnier said the deal with the UK was a "necessary step" ahead of next phase of the negotiations.
"I have worked with my team and negotiated with the UK, never against the UK," he told reporters as he arrived for the summit in Brussels.
"Now it is time for everybody to take their responsibility. This deal is a necessary step to build the trust between the UK and the EU we need to build.
"The next phase is an unprecedented and ambitious partnership. We will remain allies, partners and friends."
Arriving for the summit, European Commission president Jean-Claude Juncker said: "This is the deal. It's the best deal possible and the EU will not change its fundamental position when it comes to these issues."
Dutch prime minister Mark Rutte warned there could be no further negotiation and said he hoped the British Parliament would now back the deal.
"This is the deal on the table. I don't think there is anything more now. I don't want to contemplate a no vote. I think there will be a yes vote," he said.
"I think this is the best we can all do - both Theresa May and her Government as well as the European Union.
"I have lots of respect for Theresa May and what she has done over the last two years and particularly the last two or three weeks.
"I do think she has everything now to argue for a yes vote in the British Parliament."
Ireland's premier has said he anticipates the draft Brexit withdrawal agreement will gain approval from the EU27 member states and the UK Government in the next couple of hours to allow the process "move on".
Leo Varadkar said he was pleased to be in Brussels to sign off on the deal, which he said represented the culmination of nearly two years of work.
"It was a very difficult deal to negotiate," Mr Varadkar said.
"I anticipate that in the next couple of hours that agreement will get the assent of the 28 governments, 27 member states that are staying and also the government of the UK and that will allow us to move on."
The Taoiseach made the comments as he arrived for the European Council's special Brexit summit.
Mr Varadkar said he still regretted the fact that the UK was leaving the European Union.
"The best outcome for Ireland, and I think for Europe and Britain, would be for the UK to stay in the European Union, to stay in the single market and customs union, but we respect their decision not to do that," he said.
Mr Varadkar added: "We spent two years trying to negotiate an agreement that protects our interests, our citizens and our economy. I believe we have that: an agreement which allows for an orderly withdrawal of the UK from the European Union, an agreement which protects the freedoms and rights of citizens, particularly the Common Travel Area, an agreement which provides a transition period during which we can negotiate a future relationship."
He added: "If that isn't successful then a backstop that kicks in that assures us that there will be no hard border between Northern Ireland and Ireland. And we'll continue to have tariff free and quota free trade between Britain and Ireland which is very important for our economy."
Communities Secretary James Brokenshire told Sky News's Sophy Ridge On Sunday that MPs should back the deal when it comes before the Commons or risk taking the UK "back to square one".
"It's for MPs now, of course, to scrutinise this properly but if that does not happen then, effectively, you will be back to square one with more uncertainty, more division," he said.
"It is important for people to get behind the Prime Minister, get behind the deal that we see being approved today, allowing us to move forward as a country on to all of those things that the British people want us to do, all of the domestic priorities."
There was a clear message from people of "let's get on with it", he said.
Asked if the deal was better than EU membership he said: "It does give effect to the vote of the British people and therefore, yes, I think it is now - things have now changed, we have had that referendum, we look towards a future outside of the European Union."
Former Conservative Party leader Iain Duncan Smith said it would be "very, very difficult" to support the Prime Minister's deal arguing "far too much has been given to the EU".
He told Sky News's Sophy Ridge on Sunday: "Well I don't want to stay in the EU. I campaigned and voted to leave the EU. I don't believe that, so far, this deal delivers on what the British people really voted for, take back control of your borders, your laws, your money. I think it has ceded too much control.
"I believe the Government needs to go back and say things like 'the backstop, we simply cannot agree it and you must take all of that reference out' and things to do with the Court of Justice. That would make this a better deal, but right now the balance is definitely tilted against this being a deal, I'm afraid, that delivers on what the Government said they would deliver, which is leaving the EU and setting out to be able to do our own trade deals.
"We won't be able to do our own trade deals if we're bound into the customs union, that is single one of the most important things that people voted for."