The European Union may never again be able to conclude free trade deals if its long-awaited treaty with Canada collapses, EU leaders have said.

Canadian and European leaders have spent seven years negotiating the Comprehensive Economic and Trade Agreement (CETA), but it now looks to be in peril after a single Belgian region rejected it.

EU Commission President Jean-Claude Juncker has now invited Canada’s International Trade Minister Chrystia Freeland to attend meetings between EU leaders and officials from the Wallonia region, which is holding out against the deal.

“We need this trade arrangement with Canada,” Mr Juncker said. “It is the best one we ever concluded and if we will be unable to conclude a trade arrangement with Canada, I don’t see how it would be possible to have trade agreements with other parts of this world.”

EU President Donald Tusk also warned on Thursday night the deal could be the last negotiated by the bloc.

“If we are not able to convince people that trade agreements are in their interest… I am afraid, that CETA could be our last free trade agreement,” he said.

However, Wallonia President Paul Magnette remains defiant, telling reporters late on Thursday: “At this stage, the document is still insufficient.”

Belgian Prime Minister Charles Michel has pleaded with the region to change its mind, but under the country’s highly de-centralised constitution every region must assent to a foreign deal before the national government can approve it.

If a deal between the EU’s 500 million citizens and 35 million Canadians which has been seven years in the making were to fall apart due to the objection of a region with a population of 3.5 million, it would seriously undermine the EU’s credibility, Mr Tusk added.

The official signing ceremony is scheduled for next Thursday, with Canadian Prime Minister Justin Trudeau due to attend, but without a deal ready to sign it will have to be cancelled.

Earlier this week, Mr Trudeau suggested that the EU would be essentially pointless if it cannot even conclude a trade deal with Canada.

“If in a week or two we see that Europe is unable to sign a progressive trade agreement with a country like Canada, well, then with whom will Europe think that it can do business in the years to come?”

That failure would inevitably lead the world to ask: “What’s the point of the EU?”