Trump on Tuesday gave a conditional go-ahead for the project, which was put on hold by former president Barack Obama over environmental concerns.
Calgary-based TransCanada yesterday said in a statement it had filed a "presidential permit application" with the US State Department for approval of the project.
The 1,180-mile (1,900-kilometer) pipeline would carry oil from Canadian tar sands to US refineries on the Gulf Coast, with some 870 miles winding through the United States.
"This privately funded infrastructure project will help meet America's growing energy needs as well as create tens of thousands of well-paying jobs," TransCanada CEO Russ Girling said in a statement.
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The statement added that the project would add $3.4 billion to the US economy.
TransCanada must now wait while the US conducts a new study of the Keystone XL project. But between Trump's conditional go-ahead and his nomination of Rex Tillerson, the former CEO of ExxonMobil, as secretary of state, the project is likely to be approved.
Canadian Prime Minister Justin Trudeau recently said he wants to gradually halt exploration of the oil sands and transition away from fossil fuel.