Theresa May has asked MPs for more time for Brexit talks with the EU.
She was speaking as she updated the House of Commons in the wake of her latest efforts to secure changes to the backstop from Brussels.
EU leaders last week repeatedly insisted that the withdrawal agreement is not open for renegotiation.
Today, she said the government needs some more time for further talks with EU.
She said: "When we achieve that progress we need, we will have a meaningful vote."
However, she said if that's not achieved then MPs will have an opportunity to vote on alternative Brexit proposals on February 27th.
Last week, several key EU officials indicated they'd be open to considering Labour leader Jeremy Corbyn's call for a "permanent and comprehensive UK-wide customs union" as an alternative to the current future relationship proposals.
Open discussion w/ @theresa_may. Backstop non negotiable. We'll never abandon Ireland. I welcome @jeremycorbyn letter making a cross-party approach for the first time possible. From the hell we're in today, there is at last hope of a heavenly solution even if it won't be Paradise pic.twitter.com/2yEzINJQdb
— Guy Verhofstadt (@guyverhofstadt) February 7, 2019
Theresa May has accepted Mr Corbyn's offer for cross-party talks.
However, the prospect of remaining in the customs union appeared to be ruled out by Mrs May today.
She told MPs: "I would gently point out that the House of Commons has already voted against this, and in any case membership of the customs union would be less desirable than that which is provided for in the political declaration [on the future relationship].
"That would deliver no tariffs, fees, charges or quantitative restrictions across all sectors, and no checks on rules of origin.
"Crucially, it would also provide for the development of an independent trade policy for the UK, something that would allow us to strike our own trade deals around the world."
She concluded her speech by urging MPs to 'hold their nerve' as her government works to secure changes to the backstop ahead of the looming Brexit date of March 29th.
Responding to the statement, Mr Corbyn accused the prime minister of only offering "more excuses and more delays".
He suggested Mrs May appeared to be attempting to "run down the clock, hoping members of this House are blackmailed into supporting a deeply flawed deal".