The US Department of State said on Friday it will provide more time for relative federal agencies to review the Keystone XL oil pipeline project.

"Agencies need additional time based on the uncertainty created by the on-going litigation in the Nebraska Supreme Court which could ultimately affect the pipeline route in that state," said a statement from the US Department of State.

The 7-billion-US dollar Keystone XL pipeline, proposed by Canada's No. 2 pipeline company TransCanada more than five years ago, would run 1,700 miles (2,720 km) to connect Canada's oil sands to refineries around Houston and the Gulf of Mexico. To cross the US-Canadian border, it needs a permit by US President Barack Obama.

The project has been delayed for years as critics say it could worsen climate change by enabling further growth from the oil sands, which create higher greenhouse gas emissions than some other forms of production. In February Nebraska Supreme Court overturned a state law that allowed the pipeline to pass through the state, adding more uncertainties to the outlook of the project.

The US Department of State didn't give a deadline for the review extension, saying "the Department will give the agencies sufficient time to submit their views."

The final decision for Keystone XL pipeline was expected to come out by mid-year as the former deadline of the review period for federal agencies was in May. Today's move will likely delay a final decision on the controversial project until after the Nov. 4 mid-term elections, according to the report of local media.