The Keystone XL oil pipeline will not use American steel, seemingly contrary to a Donald Trump election pledge.
The White House has claimed this is due to the language used in a presidential directive, which applies to new pipelines or those under repair.
Sarah Huckabee Sanders, the White House spokeswoman, has said it would be difficult for US steel to be used on the Keystone pipeline as it is already under construction.
As recently as last week, Mr Trump had pledged that the Dakota Access pipeline and Keystone would not be built unless American steel was used.
The company responsible for building Keystone, TransCanada, has said the majority of the steel would come from North America, which includes Canada and Mexico.
Soon after taking office, Mr Trump used his executive powers to restart the two pipeline projects that had been blocked by his predecessor, Barack Obama.
The Keystone pipeline will run from Canada to refineries in the Gulf Coast.
It was commissioned in 2010 and has attracted a range of environmental protests. The pipeline was rejected in 2015 by Mr Obama.