Senior Conservative lawmakers advised the prime minister in phone conversations that she should delay the vote and put forward a motion describing a divorce agreement that would finally heal divisions over the issue within May's own party, according to The Times.
"As it stands her deal is going to be defeated. It has been made clear to Downing Street [the prime minister] that it would be eminently sensible to avoid that by proposing a motion that the party can support. Whether they listen or not is another matter", a senior member from the Conservative Party told the newspaper.
The prime minister has since been trying to negotiate changes to the agreement, in particular regarding the highly unpopular backstop provision, which is designed to ensure a frictionless Irish border and would, as many fear, tie the United Kingdom to the EU customs union.
May has pledged that if lawmakers reject the new version of the deal on Tuesday, the parliament would then decide whether London should withdraw without any agreement at all. If that option is voted down as well, the legislature will consider extending the Brexit deadline, currently set for 29 March.