TransCanada said Wednesday it has given up on a White House nod by year's end to proceed with construction of the northern leg its proposed Keystone XL pipeline.

In a securities filing, the company said it "no longer expects that the decision on the presidential permit required for the project will be made by year end and the corporation anticipates that its previously disclosed expected in-service date of 2013 will be similarly delayed."

The project aims to build a 1,980-mile (3,200-kilometer) pipeline from Canada's oil sands region to the US Gulf Coast.

The project was proposed back in 2008, but after years of delays, operator TransCanada split the project in two, and construction began on a southern section that does not require presidential approval.

The US State Department is currently preparing its final review of the project; it concluded in a draft report earlier this year that it would have no major impact on the environment.

The White House has so far declined to rule, citing environmental concerns.

The oil would come from Alberta's oil sands, which requires a complex extraction process that critics say would further contribute to climate warming.