She is battling adversaries in her own Conservative Party who are plotting to oust her while members of her Cabinet are pushing her get a better deal.
The terms of the UK's withdrawal have been under negotiation since June 2016 following a referendum in which 51.9% voted to leave the EU.
In his speech to the CBI, Corbyn said Labour would vote against May's Brexit deal, adding his party would not countenance a no deal Brexit.
Mr Johnson said the European Union had achieved a "very clever trick" by making Northern Ireland an "indispensable bargaining chip" in future negotiations, noting the reference to the potential need to label goods from Northern Ireland UK (NI) under the backstop proposal.
Mrs May is set to hold more talks with European Commission president Jean-Claude Junker on Saturday in a down to the wire bid to try and secure a withdrawal agreement at an emergency EU summit scheduled for Sunday.
We have made further progress.
In the meantime, EU Council president Donald Tusk is going ahead with plans to bring May and her fellow leaders together on November 25 to sign the deal.
"It is still not too late for the Prime Minister to change course", said the North Belfast MP.
Critics say it would leave Britain bound to the European Union in perpetuity and risks dividing the United Kingdom by aligning Northern Ireland more closely with the EU's customs rules and production standards than mainland Britain.
The source, speaking on condition of anonymity, praised the 62-year-old daughter of a vicar for her grasp of detail, determination and resilience.
With less than five months before Britain leaves the bloc, Prime Minister Theresa May is struggling to persuade parliament to back a draft divorce deal agreed with Brussels last week.
Asked on the Today programme whether Mrs May could win a vote on her deal now, he said: "You say ... if a vote were taken today".
Taiwan Votes in Elections Seen as Referendum on China Policy
At a campaign rally Wednesday for her party's Taipei mayoral candidate, Tsai accused China of "intervening" in the elections. The DPP is left in control of only six of Taiwan's 22 cities and counties, compared with at least 15 for the Kuomintang.
"The declaration establishes the parameters of an ambitious, broad, deep and flexible partnership across trade and economic cooperation" and other areas, according to a copy of the document seen by AFP. "The focus this week will be on the future relationship", she told Sky.
As an olive branch to those Brexit campaigners, her spokesman signalled May was open to looking at their proposed technological solutions to keep the border open on the island of Ireland.
The document envisages negotiations beginning immediately after the formal date of Brexit on March 29 2019, with high-level conferences every six months. "We shall see whether letters come in due time".
The new text was dismissed by Scottish First Minister Nicola Sturgeon as "lots of unicorns taking the place of facts about the future relationship".
"The Government's commitments under it are clear... including on Brexit".
"As we have got nearer to the point of withdrawal that has had a more material adverse impact on some companies' investment plans", he said.
As May arrived in Brussels on Wednesday to finalize the deal, European officials were hard pressed to think of any other British politician willing or able to see through an orderly, albeit painful, divorce.
He also called for the creation of a Secretary of State for "No Deal" Brexit, "with real powers across Whitehall to make things happen".
"This is a awful offer to the British people and one that the people should have the opportunity to turn down in favour of keeping our current deal as members with a say over decisions that affect our future", said Mr Umunna.
The move came after reports from Brussels that the Sunday summit could be scrapped.
The PM has faced a strong pushback from Spain over the status of Gibraltar, while France is understood to have sought amendments to wording on fishing rights in United Kingdom waters.