TransCanada, the company behind the disputed Keystone XL pipeline project, has filed a formal request to sue the US government for damages.
The pipeline, which was designed to carry oil from Canada to refineries in the US, was rejected by US President Barack Obama last November.
It would have allowed for an increase in the supply of oil from the oil sands in Alberta in Canada.
But President Obama said it was not in the "national interests" of the US.
The pipeline's construction has been hotly disputed for more than seven years, with environmentalists saying it would do irreparable damage.
The Canadian National Energy Board approved the Keystone XL pipeline in March 2010, but because it would have run across the US/Canada border, the project required a presidential permit before construction.
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http://www.bbc.co.uk/news/business-36634290This might be better in the Energy board. Don't know.