North-South structures could ensure Northern Ireland is not cut off from the European Union after Brexit, the SDLP leader has said.
Colum Eastwood said "flexible and imaginative" solutions to the border question were contained within the 1998 Good Friday Agreement which enshrined co-operation with the Republic.
The bodies established under that deal could be used to safeguard Northern Ireland's place in Europe.
Mr Eastwood said: "Post-Brexit, the North-South structures could come into their own - ensuring that we are not cut off from the broader island economy and the European Union."
Those institutions were established to satisfy nationalist demands for an Irish dimension to the Good Friday deal which largely ended violence in 1998.
They include the North South Ministerial Council and bodies dealing with issues like tourism and waterways.
Powersharing at Stormont collapsed earlier this year and there are no ministers in Belfast.
Mr Eastwood said an internal European negotiation paper effectively mapped out the need for special EU status for Northern Ireland after Brexit.
"This is a welcome and timely clarification that the trading relationship across the island of Ireland must remain unchanged in order to avoid any hardening of the border in Ireland.
"That can only happen if Northern Ireland retains full access to the single market and stays in the customs union.
"Never has a statement of the obvious been so welcome."
Lagan Valley DUP MP Jeffrey Donaldson said there are other solutions.
"It's hardly imaginative to dress up the current regulations and present them as being flexible or a solution, that simply won't work.
"It's not just Northern Ireland saying that, it's Irish farmers saying that, who don't want a customs border down the Irish Sea because a very large proportion of the food produced in the Irish Republic is exported to Great Britain."
Mr Donaldson said 72% of trade flows from Northern Ireland go via Great Britain.
He said: "The last thing we need for Northern Ireland is a border in the Irish Sea, a customs border separating us from our biggest market. That's just not feasible."
Mr Donaldson said authorities should not have to physically stop trucks at a border.