British Prime Minister Theresa May hosts EU President Donald Tusk for Brexit talks yesterday, on the eve of her keynote speech on future trade ties and amid a row over Northern Ireland.
Their meeting at Downing Street comes as the European Union prepares its position on negotiations on the future relationship with Britain once it leaves the bloc.
May is due to set out her plans in a long-awaited speech today, but it has been overshadowed by a dispute with Brussels over the status of the Irish border after Brexit.
The EU this week published a draft law codifying the divorce terms struck with Britain in December, which includes plans to avoid any customs checks on the border between Northern Ireland and Ireland.
May reacted angrily to the proposal that Northern Ireland -- part of Britain -- stay in a customs union with the EU if there is no better solution, warning she would not accept anything that risked the constitutional integrity of her country.
In a speech in Brussels yesterday morning before travelling to London, Tusk said that if the prime minister did not like the idea, she should come up with an alternative.
"In a few hours I will be asking in London whether the UK government has a better idea," he said, adding that he was "absolutely sure" EU member states would agree to the draft.
He also criticised Britain's approach to the negotiations on the future relations, saying its self-imposed "red lines" made its hopes of frictionless trade impossible.
All sides have pledged to avoid a hard border including customs checks, in order to protect the 1998 Good Friday agreement in Northern Ireland, which ended three decades of bloody sectarian violence.
The EU's chief Brexit negotiator Michel Barnier insisted the customs union plan was a "fallback" option in case Britain's two preferred options -- hi-tech frictionless border controls, or a solution linked to a future EU-UK trade deal -- fell through.
Before her talks with Tusk, May chaired an extraordinary meeting of her cabinet to discuss her speech today, amid continuing divisions over how closely Britain should remain aligned to the EU.
She has said Britain will create a new "deep and special partnership" with the EU, but has ruled out staying in its single market or a new customs union, which would require continued free movement of migrants and adherence to EU rules.
However, the opposition Labour party this week called for Britain to agree a new customs union, which it said would protect jobs and resolve the Irish question.