Ports sitting on opposite sides of a future Brexit border between Ireland and the United Kingdom are collaborating to overcome challenges that may arise when the UK exits the European Union. That move is set for March 2019.

The ports of Cork, Dublin, and Belfast also recently signed an agreement with a UN agency to work together to help ports in Africa and Asia.

Port of Belfast Harbour Master Kevin Allen said the ports of the Irish island are competitors but also “collaborators in terms of making an all-Ireland economy function and succeed.”

Brexit has created a new challenge for building an all-Ireland economy, Allen said, “But the willingness is there to make trade work.”

The 20th anniversary of the Good Friday Agreement, a peace deal that helped end many decades of political violence in Northern Ireland, was recently observed at a time when businesses and transportation companies across Europe are trying to understand how the UK’s looming exit from the European Union will affect trade routes.

The UK and the Republic of Ireland both joined the European common market in 1973, allowing importers and exporters on the island to use both countries as a gateway to other European markets. But Brexit has stoked fears of new checks and customs hurdles when goods from the remaining 27 EU member states pass through UK ports, which include Belfast, or when British goods arrive to the Republic of Ireland.

London, Dublin, and Brussels agreed in December to avoid controls on the land border between the Republic of Ireland and Northern Ireland. But according to Dublin Port Chief Executive Officer Eamonn O’Reilly in a Financial Times article, the deal didn’t cover the sea border that would come into play between the two.

The Republic of Ireland therefore plans to finish building new customs booths and freight inspection points in Dublin this year. The port currently imports about 1.3 million containers or trailers a year, of which just 200,000 must go through customs checks because the rest are shipped from within the EU.

“Once Brexit happens, 200,000 increases to one million,” O’Reilly said.