Keystone XL, as proposed, would run approximately 854 miles from Alberta, Canada to Steele City, Neb. There, it would connect to an existing Keystone oil pipeline that runs to a key trading hub in Cushing, Okla.
One section of the project needs federal approval because it would cross the U.S.-Canadian border.
Critics of U.S. President Barack Obama's energy policies said he's blocking the project's development.
White House spokesman Jay Carney, however, said the government hasn't "rejected anything."
It's delayed, he said, because of concerns about the original route through a sensitive ecosystem in Nebraska and because of "the House Republicans' insistence on including it as part of the payroll tax cut extension."
A statement from the Republican-controlled House Energy and Commerce Committee said Carney was attempting to alter the Keystone XL narrative.
TransCanada in July received the last of three permits needed from the U.S. Army Corps of Engineers to advance its 485-mile Gulf Coast Project. The project represents the domestic leg of the Keystone XL oil pipeline project. Construction started Aug. 9.