Belgium's foreign minister Didier Reynders, left, speaks with EU Council High representative Federica Mogherini during a meeting of EU foreign ministers at the EU Council building in Luxembourg, Monday, Oct. 17, 2016. European Union foreign ministers debated Monday whether to extend sanctions against the Syrian regime as political efforts to secure a cease-fire and access for humanitarian aid falter. (AP Photo/Olivier Matthys)

OTTAWA - A weekend push to persuade a small but essential pocket of Belgium to support the sweeping Canada-Europe trade agreement has yet to resolve differences ahead of a key meeting that could determine the fate of a deal deeply coveted by Ottawa.

But Canadian officials remain hopeful a solution can be found to salvage the agreement.

EU trade ministers are scheduled to hold a vote Tuesday on a pact that has the powerful backing of Europe's 28 member states and Canada, all of which combined represent about 535 million people.

"I remain cautiously optimistic about CETA — but at this point the ball is very much in the European court," International Trade Minister Chrystia Freeland told reporters in Ottawa.

"We're working hard with the Europeans ... Everyone I talked to today said: 'Hang on in there, we believe this is going to happen.' "

The path to signing the treaty, however, remains uncertain, thanks to vociferous opposition from the comparably tiny Wallonia region of Belgium — home to just 3.5 million people.

To get it done, trade ministers from all EU nations must unanimously approve the deal, known as the Comprehensive Economic Trade Agreement, or CETA. Otherwise the deal would effectively die after seven years of sometimes controversial talks.

Canadian and EU officials have been racing to persuade the Walloons to ditch their opposition to the agreement.

Last Friday, Europe's ability to unanimously approve the pact suffered a blow when Wallonia's legislature voted to reject the deal.

Opponents to the pact in the French-speaking Belgian region are concerned it would leave farmers and industrial sectors too exposed to cheaper imports from Canada. Some have cautioned it could also erode local standards for food, labour and the environment.

For the Trudeau government, signing CETA remains a top priority, and Freeland said if the deal fails "it would be a real shame."

"It would also say something quite significant about Europe's ability to conduct trade policy if they can't get it done," she said. "But we're working hard and there's still a little bit of time."

When asked if she thinks the central Belgian government will be able to convince the Walloons, Freeland said there were no guarantees.

"But I know that all of Europe except for Wallonia want this accord," she added.

Last week, Freeland dispatched special trade envoy Pierre Pettigrew, a former Liberal trade and foreign minister, to meet with Paul Magnette, Wallonia's leader.

David Lametti, Freeland's parliamentary secretary, has also met with Walloon leaders in the region for talks.

The Belgian constitution gives its three regional governments, including Wallonia, a potential veto over the deal. Without the region's support, the country's national government, which is in favour of the deal, would be unable to proceed.

The agreement has the support of all the other EU member states.

On Monday, its supporters remained hopeful the pact would survive. The decision could also spill into a gathering of EU leaders later in the week.

"I hope we will come through tomorrow," Belgian Foreign Minister Didier Reynders said Monday.

"If not, at the end of the week during the summit of EU leaders."

Next week, Prime Minister Justin Trudeau is set to fly to Brussels to sign the agreement, but only if it has unanimous backing from all the EU nations.

The deal is expected to yield billions in added trade through tariff cuts and other measures to lower barriers to commerce. At the same time, the EU says it will keep in place the strong safeguards on social, environmental and labour legislation which have given Europe some of the toughest standards in the world.

Wallonia said last week that the guarantees were not good enough and called for more talks.

— with files from Associated Press

News from © The Canadian Press, 2016