There is a threat of further port strikes in Canada as unions take their battle to a tribunal.

Canada's labour minister, Steven Mackinnon, intervened nine days ago to end lockouts of workers at the country's two biggest ports.

Mackinnon directed the Canada Industrial Relations Board to order the resumption of all operations at the ports of Vancouver and Montreal and move the talks to binding arbitration following days of closure at the two ports.

However, unions in Montreal and British Columbia are formally challenging the legal and constitutional authority of the federal labour minister to order them back to work with a panel at Canada's Industrial Relations Board set to deliberate the matter next month.

South of the border, a pressing issue for the incoming Donald Trump administration could well be another strike across the US east and Gulf coasts with a trade union refusing to budge on the issue of automation.

Following a three-day strike at the start of last month, the International Longshoremen's Association (ILA) reached an agreement with the United States Maritime Alliance (USMX) on wages, suspending their walkout until January.

Both sides returned to the bargaining table earlier this month to negotiate outstanding issues with their existing contract due to expire on January 15, five days before Trump takes office.

USMX in a release yesterday said on November 13 negotiations on the master contract had broken down again once again, hiking the risk of another strike in the new year.