She's under pressure from her MPs to not to give any further ground in negotiations, and even to try and win some clarifications to the draft withdrawal deal agreed with Brussels.
EU leaders meet in Brussels on Sunday to sign off on a Brexit deal.
Mrs May would then have to put that to the UK's Parliament.
UK correspondent Olly Barratt says her visit to Brussels is being closely watched.
IN: "Theresa May…
OUT: ….back me."
DUR: 77 seconds
http://www.fsnradionews.com/feeds/1121brexit-ob1.mp3
ALT:
UK correspondent Olly Barratt says it's possible there could end up being more than one parliamentary vote on the deal.
IN: "There is…
OUT: ….the moment."
DUR: 40 seconds
http://www.fsnradionews.com/feeds/1121brexit-ob2.mp3