Britain's hopes for a successful Brexit could be about to be destroyed by a single region of Belgium
The 28-nation bloc has spent over seven years negotiating a free-trade deal with Canada - referred to as the EU-Canada comprehensive economic and trade agreement (CETA).
The deal now just needs to be ratified by all EU member states.
However, Wallonia, one of Belgium's six legislatures, has vetoed the deal, meaning Belgium's national government cannot give the CETA its approval. Paul Magnette, the leader of the Wallonian parliament, said: "We cannot sign by Friday."
However, unless Wallonia lifts its veto by the end of today, the deal will collapse, leaving Britain's hopes of negotiating a similar deal once it withdraws from the EU in tatters, according to European Council President Donald Tusk.
"If you are not able to convince people that trade agreements are in their interests . . . we will have no chance to build public support for free trade and I am afraid that means that CETA could be our last free trade agreement," he said.
Tusk's remarks were echoed by Cecilia Malmstrom, the EU's trade commissioner. Speaking earlier this week, the Swede said: "If we [the EU] can't make it with Canada I'm not sure we can make it with UK."
Wallonia's power to stand in the way of an entire international trade agreement is just another reminder of how difficult making a success of Brexit negotiations is going to be for Theresa May's government.
Belgium, like other EU member states, operates under a federalist political system. This means that significant powers are granted to regional governments, allowing them to block legislation at the national level.
In other words, Britain does not just need European leaders to agree to post-Brexit trade deals, but regional legislatures across the continent. It is a massive undertaking.
Labour MP Stephen Kinnock, who lived and worked in Brussels before entering Westminster politics, touched upon this when Business Insider interviewed him last week.
He said: "What you have to recognise that is after Article 50 is done, the next step of negotiations is agreement by an absolute majority in the European Parliament and ratification in all 27 member state parliaments. I would be absolutely amazed if you could do that in less than a year.
"You only need the Slovenian parliament, for example, to say 'actually, we don't like what's just been agreed on the tariffs on automobiles' and it all gets held up in the Slovenian Parliament," he added.
"I think that's one of the reasons why hardcore Brexiteers are pushing for the hard version."
May is currently in Brussels where she is meeting with European leaders to discuss issues like the Syria crisis, Russian aggression, and Britain's imminent departure from the 28-nation bloc.
She reassured leaders that Britain is committed to playing a "full role" in EU decision-making and strategy until it completes its formal withdrawal.