The European Union cleared the way Friday for Brexit talks with Britain to move onto the second stage but it warned that the discussions on trade and other matters relating to their future relationship will be "dramatically hard". But there is hard work and uncertainty ahead when negotiations resume in the new year.
Mrs May is set to discuss her vision of the "end state" for the United Kingdom outside the European Union at a cabinet meeting on Tuesday, having suffered her first Commons Brexit defeat earlier this week.
Talks on phase two are set to begin in January. But the European Union also wants to hear more from London about how it sees their future relations - a subject on which the British government itself is divided.
And they state that the European Union is now ready only to engage in "preliminary and preparatory discussions with the aim of identifying an overall understanding of the framework for the future relationship" after additional guidelines have been adopted at a future summit in March.
The prime minister said it was important to work out the exact terms of an implementation period, created to soften the effects of Brexit after the March 2019 leave date, 'as soon as possible.to provide invaluable certainty for employers'. However, it would still have to obey EU laws and respect the primacy of the European Court of Justice.
"We can not be a colony of the European Union for two years from 2019 to 2021, accepting new laws that are made without any say-so of the British people, Parliament or Government", he told BBC's Newsnight.
He said the deal sought by the Government would mean while the United Kingdom "technically" leaves the customs union and single market, it will keep the same rules for trade and immigration until 2021.
Questions still linger however over the divorce agreement, after Brexit minister David Davis appeared to suggest it was not legally enforceable and that Britain would only pay its exit bill if it got a trade deal.
Hammond said his government would try to secure a close arrangement specific to Britain.
The short answer is no.
With Cabinet ministers due to discuss their preferred "end state" relationship with Europe for the first time on Tuesday, pressure is mounting on Mrs May to deliver a detailed statement on her aims which the European Union will regard as an adequate basis to enter swiftly into substantive talks.
They confirm that agreement on a future trade relationship can only be finalised once the United Kingdom has formally left the EU. The EU is also wary of granting the United Kingdom any special trade concessions, because it has clauses in trade pacts with other countries that would force the bloc to update those deals to match.
A British government official said the prime minister made "no secret of wanting to move on to the next phase and to approaching it with ambition and creativity".
At Friday's meeting, the leaders said Friday "sufficient progress" had been reached on the outstanding European Union bill Britain will have to pay, the rights of citizens in each other's areas and the commitment to maintain a transparent border between Ireland and Northern Ireland. A separate stream of negotiations on this issue alone will continue throughout the second phase. With so little time left before Brexit is due to take place, negotiators face a tight deadline to carve out a wide-ranging separation deal. Everything has to be wrapped up next fall to leave time for parliaments to ratify any final Brexit deal before March 2019.