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She pointed out that countries tended to trade mostly with their neighbours, adding: "I think geography talks very loudly".
The United Kingdom is due to leave the European Union on March 29 and yet little is clear: There is, so far, no full exit agreement and some rebels in May's Conservative Party have threatened to vote down a deal if she clinches one.
Michel Barnier, the EU's chief Brexit negotiator, is working on a revised plan for Northern Ireland that would involve technology-based solutions to avoid a hard border for goods.
Theresa May has warned MPs if they vote down her Brexit deal then the United Kingdom will crash out of the European Union with no deal at all.
That has led to worries that Britain is heading for a "no-deal Brexit" that would see it revert to World Trade Organisation rules on trade and force it to pay tariffs on goods imported from the EU.
That includes a vote in the British Parliament, where May's Conservatives don't have an overall majority and where her Brexit blueprint faces opposition from both pro- and anti-EU lawmakers.
May is calculating that, faced with a stark choice between an imperfect agreement and the unknown territory of "no deal", many lawmakers will grudgingly back her proposals.
"It's ensuring that we get that good deal from the European Union which is good for people in the United Kingdom, wherever they live in the United Kingdom, that's what's important for us".
Brexit briefing Michel Barnier at meeting in Brussels yesterday
That outcome is far from certain.
Prime Minister Theresa May has struggled to bridge a deep divide within her Conservative Party about how close a relationship Britain should have with the EU. Anti-Brexit campaigners are also pushing for a public referendum on the divorce agreement.
"Unless we do that. much of the point of Brexit is nullified".
The rival tipped by bookmakers to succeed May, Boris Johnson, attacked May's Brexit plans, known as Chequers after the country house where they were hashed out in July.
"The whole thing is a constitutional abomination, and if Chequers were adopted it would mean that for the first time since 1066 our leaders were deliberately acquiescing in foreign rule", Johnson said, referring to the 11th Century invasion which established Norman rule over England.
Britain is due to leave the European Union in little more than six months' time but London and Brussels have yet to strike a deal to secure a transition period.
The IMF predicted Britain's economy would grow by about 1.5 percent a year in 2018 and 2019 - lagging behind Germany and France - if a broad Brexit agreement was struck.
In a recent interview with Sky News, International Trade Secretary Liam Fox said it was not a question of increasing immigration for non-EU citizens but to ensure that a "level playing field" was created to ensure that non-EU citizens would have a "better chance of getting access" to the United Kingdom within the government's immigration targets.