May is under pressure from eurosceptics in her Conservative party to keep her promise of a clean break with the European Union, but is also running out of time to reach a deal with Brussels.
After meeting a number of European leaders last week in London and on the sidelines of an EU summit, she will meet Dutch Prime Minister Mark Rutte and then German Chancellor Angela Merkel.
Then on Friday, she takes her divided cabinet away for the day to her Chequers country retreat in a bid to thrash out their differences on how close economically Britain should stay to the EU.
Less than nine months before Britain leaves the European Union in March 2019, the government has yet to set out exactly what it wants, and progress in the negotiations remains slow.
Updating the House of Commons on the EU summit, May was questioned by eurosceptic Conservative MPs about her stance, where she repeated her plans to leave the EU's single market, customs union and courts system.
She insisted Brexit would happen as planned on March 29, 2019, but dodged a question about extending the transition period, currently limited to December 2020.
The divisions in her party were laid bare earlier by an intervention by leading eurosceptic MP Jacob Rees-Mogg, who warned she must stick to her promises or risk the government collapsing.
Foreign Office minister Alan Duncan accused him of "threatening" May, saying: "The ideological right are a minority despite their noise and should pipe down."
But eurosceptic Foreign Secretary Boris Johnson, tweeted that it was "vital that all MPs are able to air their views", describing Rees-Mogg as a "principled and dedicated MP".
Opposition Labour leader Jeremy Corbyn told the Commons: "The prime minister is stuck in the middle of two warring factions. But she now needs to pick a side."
He added: "The divisions and open warfare at the highest level of her government are holding the country back."
May insisted she was delivering the result of the 2016 referendum to leave the EU, saying: "I have picked the side of the British people."
One of the crucial issues to be discussed at Friday's cabinet meeting is how to create a new customs relationship with the EU that avoids border checks between Northern Ireland and Ireland.
Ministers have been mulling two possible options for months, both of which have faced opposition in Brussels and within the cabinet, and media reports suggested Monday that a third option was now being considered.
Once ministers agree, the government will next week publish a policy document setting out in detail what it wants from the future trading relationship.
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