OTTAWA — While much of the world may be focused on President Trump’s threats of a trade war with China, Canada’s attention right now is on a commercial feud within its own borders.

The provinces of British Columbia and Alberta are locked in a battle over a $7.4 billion expansion of a pipeline that runs from Alberta’s oil sands to a tanker port near Vancouver, a plan approved long ago.

Many British Columbians fear that increased tanker traffic could lead to spills along a coastline that is a global tourist attraction. Alberta argues that the pipeline is vital to its energy industry and the entire Canadian economy.

The rhetoric and threats from both provinces has often been intemperate, and the dispute has put Prime Minister Justin Trudeau in a difficult situation, forced to choose sides in an argument that boils down to the economy on one hand and the environment on the other.