Leaders of 27 EU countries' gathered on Sunday to endorse both a detailed treaty setting out the terms on which Britain will leave the European Union and a declaration outlining how Britain can keep close to its biggest market by following many EU rules after a two-to-four-year transition.

"There was no applause, no flowers and everyone said it was an unhappy day."

"There is no plan B. This is the deal on the table and I'm not willing to contemplate defeat in the British parliament because I have every confidence in Theresa May and the wisdom of the British people."

"I can only tell you in all honesty what the situation is and the situation is that there is no plan B. This is the deal on the table. If anyone thinks in the United Kingdom that by voting 'no' something better would come out of it, they are wrong. This is the best we can get for both the European Union and the United Kingdom."

"You can certainly say it was a historic summit and a historic day, which produces mixed emotions. It is tragic that Great Britain leaves the EU after 45 years but we have to respect the vote of the British people and, based on this, it is good that we agreed on a withdrawal agreement and a political declaration about future ties with Great Britain."

What if deal rejected by UK parliament?

"This is a speculative question that I cannot answer. We have committed to something in a very difficult situation and I think that Theresa May, as British prime minister, will do everything she can to play her part and so we are concentrating on completing the course we have set ourselves on."

"The negotiations to date have been difficult and for the current and future ones we should base ourselves on the motto 'where there is a will, is there a way'. In this tragic and sad situation, what is good is that we have gone down a difficult path with this withdrawal agreement and that should give us assurance and strength so that we can sort out the future relations too."

“We must draw all the consequences that show that the European Union has a fragile side, it can be improved …. It shows that our Europe needs to be rebuilt and that is the option I support and will continue to work toward.”

“On the issue of fishing, of reciprocal access, our fishermen will be well protected, that is a priority in our future relationship, reinstated in the text and very present in today's conclusions.”

“It's not a day when we should celebrate, nor a day of mourning. It is the choice of a sovereign people.

DUP, which props up May's minority government, has said it would try to block the deal because it binds London to many EU rules and the DUP fears it could weaken the province's ties to Britain.

DUP leader Arlene Foster said she would “review” the agreement to back May's Conservative government if the Brexit divorce is passed by Britain's parliament.

“The European Parliament will stress its role (referring to any extension of the transition period)... Changes cannot be made without the due involvement of the European Parliament.”

“Today is not a good day”

Asked what would happen if UK parliament rejects deal: “It's impossible to re-open the text.”

“It is a sad day. Seeing a country like Great Britain, but I would say this of any others, leaving the European Union is not a moment of jubilation or celebration. It is a sad moment, a tragedy.”

“I believe that the British government will succeed in securing the backing of the British parliament.”

“I would vote in favor of this deal because this is the best deal possible for Britain.... This is the deal. It is the best deal possible and the European Union will not change its fundamental position when it comes to this issue.”

“All along this extraordinary negotiation, very difficult we have worked to reach a deal. That means to organize in an orderly fashion the withdrawal decided by the UK. We have negotiated with the UK, never against the UK. Now it is time for everybody to take their responsibility, everybody. This deal is a necessary step to build trust between the UK and the EU, we need build in the next phase of this unprecedented and ambitious partnership. We will remain allies, partners and friends.”

(Cover photo by CGTN's Du Chenxin)