Speaking immediately after the vote in the British Parliament, a spokesman for European Council president Donald Tusk said the backstop was part of the withdrawal deal and was not up for negotiation.
Facing the prospect of another doomed vote in the British Parliament, she agreed on Tuesday to take her draft "Brexit" plan back to Brussels to try and get the Europeans to accept changes to a key provision on the Irish border.
The Prime Minister is preparing for another battle in Parliament this afternoon as MPs vote on a series of amendments to her Brexit plan. They do not want a so-called backstop provision that would keep Britain in a customs union with the EU in order to keep open the border between Northern Ireland and EU member Ireland.
And Mr Johnson raised hopes of the amendment winning a majority in Tuesday evening's votes by tweeting: "If the Prime Minister indicates in the debate that she will be pressing Brussels to reopen the Withdrawal Agreement to make changes to the backstop, I will gladly support the Brady amendment".
"There is a very clear message from the EU's leaders that they want (Britain) to leave with a deal, and they understand this is in the best interests of the European Union as well as the United Kingdom", he said.
The former minister Caroline Flint and Laura Smith, the MP for Crewe and Nantwich, joined with the veteran Eurosceptics Kate Hoey, Graham Stringer and Dennis Skinner in voting down Yvette Cooper's amendment by 321 votes to 298.
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Numerous killings involved sexual assaults and ligatures, Cantlon said, adding that some also included confinement with ropes. When he suddenly went missing the day after Toronto's gay pride parade, his friends noticed quickly, and so did the police.
May's initial deal was crushed by a humiliating defeat in Parliament two weeks ago, and she survived a subsequent no-confidence challenge on a party-line vote.
If passed it could serve as a first step toward a compromise - known as the Malthouse plan - being discussed by the Cabinet today. She said when she returns to Brussels she needs the strongest voice behind her, adding that the amendments "provide a cacophony of voices when we need just one".
May has already spent months trying to amend the backstop with no success, but has promised to return to Brussels if that is what her MPs want.
The British PM has opened a day of debates on competing proposals about what to do next following the rejection of her deal earlier this month.
Parliament will vote on proposed changes to May's beleaguered Brexit plan from 7 p.m. London time, with Speaker John Bercow choosing which amendments get picked.
The EU insists the backstop can only be ditched if the United Kingdom stays in a customs union with the bloc.
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As member station WBHM reports , many school systems and city and county offices have since been closed due to expected snow. Plows were working overtime in Cedar Rapids, Iowa overnight where heavy snow made roads almost impassable for drivers.
She had issued a plea for MPs to give her a clear "mandate" to reopen the Withdrawal Agreement which she agreed with the European Union last November and seek to secure changes to its controversial backstop provision.
Prominent Brexit-supporting lawmaker Jacob Rees-Mogg has said that May's deal could be made acceptable to eurosceptic rebels in the Conservative Party if the Irish backstop was removed or nullified.
Numerous MPs have put forward amendments for debate on Tuesday rejecting this "no deal" scenario, and calling variously for Brexit to be delayed, negotiations be reopened with the European Union, or a second referendum.
"While we have been working closely with our suppliers on contingency plans it is not possible to mitigate all the risks to our supply chains and we fear significant disruption in the short term as a result if there is no Brexit deal".
May's approach drew praise from Brexit-backing lawmakers but prompted scorn from their pro-EU colleagues.
Labour leader Jeremy Corbyn has refused to enter talks with May until a No deal is ruled out.
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He contends that Maduro's re-election to a second six-year term was fraudulent. Guaido has won wide worldwide support, including from the United States.
Tuesday's votes are the latest twist in the turmoil that the Brexit vote has unleashed in one of the world's top economies.