OREANDA-NEWS. Canadian midstream company TransCanada said it will file a claim under the North American Free Trade Agreement (NAFTA) seeking $15bn in damages stemming from the US administration's decision to reject its proposed 830,000 b/d Keystone XL pipeline.

TransCanada also filed a lawsuit in the US federal court in Houston, claiming that the White House overstepped its constitutional powers in rejecting its $8bn project to transport crude from Alberta's oil sands and the Bakken formation to Nebraska and then onward to US Gulf coast refiners.

TransCanada expects to have to wait at least six months to take action under its NAFTA claim. The legal filing today gave the State Department notice it was pursuing a claim, which sets up an arbitration process.

The company today said the US State Department's rejection of the pipeline in November was not based on its merits but was a "purely symbolic" gesture intended to demonstrate US leadership to address climate change.

TransCanada said it expects to take a write-down of C$2.5bn-$2.9bn ($1.8bn-$2.1bn) to its fourth quarter results to reflect its lost investment in the project, which had been in process since 2008.

TransCanada in its lawsuit argues that President Barack Obama exceeded his constitutional authority when he overrode the will of the US Congress. Congress in February 2015 passed a bill that aimed to force approval of the pipeline, though Obama vetoed it and stopped it from taking effect.

TransCanada's lawsuit claims the legislative action from Congress supporting the pipeline should displace Obama's action blocking construction. TransCanada has asked the court to find Obama did not have legal authority to stop it from building the pipeline, and to prevent the US administration from taking further actions to slow down construction.

TransCanada's NAFTA claim said the US damaged the company's investors by unjustifiable delaying a decision on a permit for seven years, then denying the permit because of the perception that it would result in higher greenhouse gas emissions.

US secretary of state John Kerry had said a key factor behind the rejection was its potential to undermine the US' ability to fight climate change. Environmentalists vehemently opposed the pipeline because of concern it would boost production of oil sands and increase greenhouse gas emissions.

The State Department did not respond for comment.