The Canadian company that proposed the Keystone XL oil pipeline says it has filed a lawsuit over the US government's rejection of the project.
It also plans to file a second legal challenge that will seek more than $US15 billion ($A21.24 billion) in damages.
TransCanada filed a federal lawsuit in Houston alleging US President Barack Obama's decision in November to kill the pipeline exceeded his power under the country's constitution.
The company announced on Wednesday it will submit a separate petition seeking the billions in damages, alleging the US breached its obligations under the North American Free Trade Agreement.
In November, Obama quashed the pipeline, declaring it would have undercut US efforts to clinch a global climate change deal.
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The president said he agreed with a State Department conclusion that Keystone wouldn't advance US national interests.
"TransCanada has been unjustly deprived of the value of its multibillion dollar investment by the US administration's action," TransCanada said in a statement.
"As the administration candidly admitted, its decision was not based on the merits of the project. Rather, the denial was a symbolic gesture based on speculation about the (false) perceptions of the international community regarding the administration's leadership on climate change."
In its lawsuit, TransCanada alleges Obama's decision exceeded his powers as president and infringed upon congress' power under the US constitution to regulate interstate and international commerce.
