The First Minister said she would be “astonished” if MSPs do not refuse legislative consent for the EU Withdrawal Bill on Tuesday.
“What happens after tomorrow’s vote, [is] the ball is in the UK government’s court,” the First Minister said at a Q&A event in London.
“They have to decide to ignore the views of the Scottish parliament or listen and try very hard get a deal that closes the gap that remains between us.”
She added: “Much of the progress is intended to be in an agreement and we are being asked to take on trust quite a lot. It strikes me that if the UK government decides to carry on regardless, then we were right not to take this on trust.”
The First Minister said there was a “realistic possibility” that Theresa May could be forced by MPs to accept continued membership of the EU customs union after Brexit.
But she warned that with time running out, there was a risk that the “whole process crashes before that can emerge”, sending the UK crashing out of the EU without a deal.
Ms Sturgeon said she was “trying to cling on to some hope” that a deal could be done over who controls 24 powers in devolved areas including agriculture, fisheries and the environment.
The First Minister said she was still open to striking a deal with the UK Government over control of devolved powers returning from Brussels after Brexit, saying Tuesday’s vote could be “overturned” in the event of a last-minute breakthrough.
But she added that “at the eleventh hour… it doesn’t look particularly promising”.
Ms Sturgeon said the Tories, who are expected to be the only party to support the Withdrawal Bill, would be left “isolated” in Holyrood by their backing for Brexit.
The First Minister told a business audience at the headquarters of wire service Reuters that any kind of Brexit deal would advance the case for a second Scottish independence referendum, adding that she doesn’t believe independence “will ever be off the table until it’s a reality”.