Washington (AFP) - The US Congress will vote in coming days on approving construction of the much-delayed Keystone XL oil pipeline, a project Republicans claim is step one in their plan for enhanced US energy production.

Should the Senate next Tuesday approve the same bill that the Republican-led House is widely expected to pass this Thursday, the controversial measure would head to President Barack Obama's desk, some six years after its initial consideration.

Obama's administration for years has held up approval of the $5.3-billion pipeline that would transport Canadian tar-sands oil to US refineries, citing the potential environmental impact.

The Senate's Democratic leadership has largely bent to Obama's wishes in preventing a Keystone vote.

But Republicans, and several Democrats in energy-industry states who also back the project, saw an opening in the aftermath of last week's midterm elections in which the GOP routed Obama's party and snatched the Senate majority.

"I believe it is time to act," Senate Democrat Mary Landrieu, who is locked in a close run-off race for her Louisiana seat, told Senate colleagues Wednesday.

Landrieu, who chairs the Senate Energy Committee, stressed the bill now had the necessary 60 votes to overcome blocking tactics by her fellow Democrats in the 100-member chamber.

Incoming Senate Majority Leader Mitch McConnell praised Democrats for having "finally backed off" their objections to a Keystone vote.

"The American people have elected a new Republican majority in the Senate and that has already made a difference," McConnell said in a statement.

"I hope this post-election conversion on Keystone signals Democrat cooperation on a whole host of other energy bills they have blocked, and whose passage would help to make America more energy-independent."

The House of Representatives already voted in May 2013 to authorize the pipeline but it stalled in the Senate.

The White House threatened a veto of similar Keystone legislation last year, but Landrieu suggested she believed Obama might relent.

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The issue could signal a bright spot in cooperation between the warring parties.

The House's Keystone bill was introduced Wednesday by congressman Bill Cassidy, who is challenging for Landrieu's seat in their December 6 runoff, and both lawmakers are eager to appear as the dealmaker who rammed Keystone through Congress.

A southern segment of the pipeline that needed no presidential action is now under construction by builder TransCanada.