MPs are weighing up what Theresa May says are “legally binding” changes to her Brexit deal as they prepare to vote on it for the second time.
The PM says concerns that the Irish backstop, an insurance policy designed to avoid a hard border in Ireland, may “become permanent” have been addressed.
Attorney General Geoffrey Cox has published his updated legal advice before making a Commons statement.
Labour said the PM had secured nothing new and they would vote against.
The last time Mrs May’s withdrawal agreement was put to Parliament in January, it was voted down by a margin of 230.
The BBC’s political editor Laura Kuenssberg said it would be a “political miracle of historic proportions” if Mrs May could overturn such a heavy defeat.
The PM will address a meeting of Tory MPs at 11.30 GMT.
An hour later, Mr Cox will face MPs to tell them if he has changed his opinion on the backstop, having concluded in December that the UK would not be able to leave the arrangement of its own accord and there was nothing in law to stop it “enduring indefinitely”.
The government’s senior law officer, whose advice has been shown to cabinet, has strongly dismissed suggestions he told ministers on Monday his view had not changed and he had been told to go away and think again.