WASHINGTON (CNN) -- The Senate narrowly rejected a Republican-sponsored measure Thursday afternoon, that would have bypassed the Obama administration's current objections to the Keystone XL pipeline and allowed construction on the controversial project to move forward immediately.
Fifty-six senators voted in favor of the amendment -- four short of the 60 required for approval. Eleven Democrats joined a unanimous Republican caucus in backing the plan.
The proposed 1,700-mile long pipeline expansion, intended to carry crude oil from Canada's oil sands through Kansas to the U.S. Gulf Coast, has become a political lightning rod. Supporters, including the oil industry, say it's a vital job creator that will lessen the country's dependence on oil imported from volatile regions.
Opponents say the pipeline may leak, and that it will lock the United States into a particularly dirty form of crude that might ultimately end up being exported anyway. The measure has sharply divided key Democratic constituencies. Labor unions largely back the plan while environmentalists oppose it.
President Barack Obama rejected a bid in January to expedite the pipeline, arguing that a decision deadline imposed by Congress did not leave sufficient time to conduct necessary reviews. Administration officials have said the president may still eventually give the project a green light, though critics accuse him of trying to delay a final decision until after the November election.
Obama personally lobbied wavering Democrats to block passage of the amendment.
"He made some calls," White House Press Secretary Jay Carney told reporters before the vote. "The president believes that it is wrong to play politics with a pipeline project whose (exact) route has yet to be proposed."
While the amendment would have approved the construction of most of the pipeline expansion, it would not have allowed any work to begin immediately in Nebraska. Dave Heineman, Nebraska's Republican governor, cited environmental concerns in opposing the original route of the proposed expansion.
Congressional Republicans blasted the president for twisting the arms of fellow Democrats.
"By personally lobbying against the Keystone pipeline, it means the president of the United States is lobbying for sending North American energy to China and lobbying against American jobs," House Speaker John Boehner, R-Ohio, said at a news conference.
Senate Minority Leader Mitch McConnell, R-Kentucky, said Obama is "out of touch" on the issue.
"At a moment when millions are out of work, gas prices are skyrocketing, and the Middle East is in turmoil, we've got a president who's up making phone calls trying to block a pipeline here at home," he said. "It's unbelievable."
Republican presidential front-runner Mitt Romney called the decision a "no-brainer."
"How in the world can you have a president who doesn't understand the importance of getting energy from our next-door neighbor?" he said.
Democratic opposition to the Republican measure was complicated by reports last week that former President Bill Clinton came out in favor of building the pipeline.