"To turn commitments into agreements".
This is especially important when it comes to Ireland.
Mr Juncker said the controversial "backstop" proposal for dealing with the Northern Ireland Border "translates faithfully" the agreement reached between Ms May and the European Union in December.
"If nerve gas was actively used against civilians in one of our member states, I believe that the European Council should, in clear terms, express its full solidarity with the British people and the British government in addressing this issue", said Timmermans, who as Dutch foreign minister accused Russian Federation of downing an airliner flying from Amsterdam over Ukraine in 2014.
Britain is due to leave the European Union on March 29, 2019 but is looking to agree a transition agreement for a period after Brexit in order to smooth out the impact.
"We are calling for a basic decision on this issue on the part of the EU and the British Government at the European Council meeting".
Several issues remain to be solved, including finding a solution for the future of the Irish border.
In the speech May suggested Britain would commit to keeping some European Union regulations and standards while reserving the option to diverge in others.
Barnier also made it clear that if Britain wanted to remain in some European Union agencies like those on chemicals, aviation or medicines, it would also have to recognize the authority of the EU's top court in those areas.
The agreement would be based around four "pillars" - trade, foreign policy and security cooperation, internal security and "thematic" cooperation, which includes education and research programmes.
The European Parliament's Brexit co-ordinator Guy Verhofstadt, meanwhile, called for the United Kingdom to move beyond "slogans" and "soundbites".
An association agreement would give "a vision, an architecture" to post-Brexit relations and avoid a repetition of the complex web of individual agreements the European Union has with Switzerland.
Michel Barnier said any attempt by Britain to gain a competitive edge through the use of what is termed "dumping" would jeopardize hopes the country has for a smooth and orderly withdrawal from the EU.
"We are open for business".