WASHINGTON Six Republican senators, including Senate Minority leader Mitch McConnell, formally filed an amendment on Monday to a highway funding bill that would approve the Keystone XL oil pipeline.
It is the latest move in an uphill battle by Republicans to advance TransCanada's $7 billion project after President Barack Obama last month said it should be put on hold pending further environmental reviews of a new route for its Nebraska portion.
Republicans want to make Obama's rejection of the pipeline and the thousands of construction jobs that it would create an issue in the 2012 presidential election.
Along with McConnell, the amendment was filed by Republican senators John Hoeven, Richard Lugar, David Vitter, Mike Johanns and Orrin Hatch.
It is not yet clear whether senators will get to vote on the measure. Senate leaders are still negotiating which amendments will get a vote. If the Keystone measure makes it to the Senate floor, it would require 60 votes to approve.
There are currently 47 Republicans in the U.S. Senate, although a number of Democrats have said in the past they support the pipeline.
Environmental groups have fought the pipeline tooth and nail, arguing that it would increase pollution from Canada's oil sands production and that jobs estimates are inflated.
On Monday, they told reporters they would pressure Democratic senators to stand by Obama's decision.
The groups are planning to deliver at least 500,000 electronic signatures to Senate leaders this week to protest the Keystone amendment.
"Our members are fired up about this," said Michael Brune, executive director of the Sierra Club, in a call with reporters.
The Republican-controlled House of Representatives is also set to consider its version of the highway bill this week. It includes a provision that would direct the Federal Energy Regulatory Commission to give a permit to the pipeline within 30 days.
Congress has been unable to agree on long-term funding for transportation since 2009 and has relied on a series of temporary spending bills. The current one expires on March 31.
Even if the Democratic-controlled Senate passes the amendment and the Senate and House agree on a highway bill that includes the Keystone provision, the bill would still need to have Obama's approval to become law.
The finance minister for Canada's top oil producing province of Alberta told Reuters on Monday he expects the pipeline project to be "revived and approved" following U.S. presidential elections this year.
(Editing by Jim Marshall)