Protesters participate in an anti-Keystone pipeline demonstration in New York's Foley Square on November 18, 2014

A US state high court on Friday overturned a ruling that had blocked construction of the Keystone XL oil pipeline, giving a dramatic victory to supporters of the controversial project.

The decision by Nebraska's Supreme Court reversed a 2012 ruling that determined that the governor had violated the state's constitution by bypassing Nebraska regulators and approving the route of the Canada-to-US pipeline.

"On appeal, the state contends that the landowners lacked standing to sue and that L.B. 1161 is constitutional," the court said in a statement, referring to law which allows major oil carriers to bypass regulatory procedures.

The high-court ruling increases the likelihood that Keystone—originally proposed in 2008 by builder TransCanada—will ultimately be constructed and allow crude oil from Alberta to be transported south to refineries on the US Gulf Coast.

President Barack Obama has declined to sign off on the project, expressing environmental concerns.

But Republicans in Congress see Keystone as a top priority and have been pushing to pass legislation that would authorize construction of the project without need for Obama's approval.

Republicans now control both chambers of Congress and passage of a Keystone bill is expected.

The House of Representatives votes on such a measure later Friday, and the Senate begins debate on it next week.

Map of the US showing the route of the Keystone XL pipeline

The White House has signaled Obama would veto the measure if it reaches his desk.

The Nebraska judges voted 4-3 in favor of upholding the earlier ruling that blocked the Keystone construction, but Nebraska's Supreme Court requires a five-vote majority and it fell one vote short.

"L.B. 1161 permits these pipeline carriers to obtain approval from the governor to exercise the power of eminent domain for building a pipeline in Nebraska," the court said.

Congressional Republicans were quick to applaud the ruling.

"Today's decision wipes out President Obama's last excuse," Senator Lisa Murkowski, chair of the Senate Energy and Natural Resources Committee, said in a statement.

"He's had six years to approve a project that will increase US energy supplies and create closer ties with our nearest ally and neighbor, and he's refused to act," she added.

"Regardless of whatever new excuse he may come up with, Congress is moving forward."