"Traders will now be watching what the European Union officials say after their comments on Wednesday that a transition agreement is far from agreed", said Viraj Patel, an FX strategist at ING in London.
"It is possible to have that frictionless trade that we all want, that prosperous economy, at the same time as getting back control of our destiny", he said.
"Our responsibility is to work positively with Britain to explore solutions but if we can't agree solutions then what we have, of course, is the backstop which is a commitment by the British government to maintain full alignment with the rules of customs union and the single market", he said.
May told the leaders late Friday the United Kingdom would seek "customs arrangements that would lead to as frictionless trade as possible with our European neighbors, as well as ensure no hard border between Northern Ireland and Ireland", a Downing Street spokesman said Saturday.
May rejected an EU proposal to keep Northern Ireland in the bloc's customs union to ensure there is no need for border infrastructure with the Irish republic after Brexit.
British Prime Minister Theresa May gave a speech on what her government is looking for, to which some responded that what how she will achieve those goals is still anything but clear.
"We are leaving the single market, life will be different", said Theresa May.
But senior Tory Sarah Wollaston, one of the MPs who has signed Ms Soubry's amendment, said the rebels would now give the Prime Minister "breathing space" to try to negotiate her own customs plan.More news: Rick Ross reportedly hospitalized, on 'a form of life support'
The speech was as much about tone as it was about laying out Britain's negotiating position.
But her vision was little changed from an earlier proposal for Britain to be able to diverge from some of the EU's rules and regulations while sticking to others which benefit Britain, a plan the bloc has described as "pure illusion".
The British Prime Minister has committed to leaving the EU customs union which guarantees tariff-free trade, but insists a hard border can be avoided through technological solutions and placing no new restrictions on the 80% of cross-frontier trade carried out by smaller businesses. "We will not be buffeted by the demands to talk tough or threaten a walk-out", she said.
Michel Barnier said: "Clarity about the United Kingdom leaving the single market and customs union and recognition of trade-offs will inform EU Council guidelines re: a future free trade agreement".
Now the International Trade Secretary has come forward and said Labour's stance would result in Britain being "rule takers with no say in how they were made".
Scottish First Minister Nicola Sturgeon, an opponent of Brexit, said May could no longer get away with "vacuous, meaningless rhetoric".
"We chose to leave".
May, 61, has long kept her cards close to her chest, trying to avoid provoking those in Britain who want a clean break with the European Union, or others who fear the world's sixth-largest economy will suffer if barriers are raised against a major trading partner.
That could be seen by the European Union as cherry-picking benefits of membership, something it insists Britain can't do.