The Obama administration announced today that it would study alternate routes for the controversial Keystone XL pipeline, kicking a politically contentious issue down the road past the 2012 election.

The State Department, which conducts the impact study of the proposed project, said today that it will take an additional 12-18 months to consider alternate routes in Nebraska, where environmental activists worry a giant underground aquifer might become contaminated if the pipeline passes over it.

President Obama issued a statement welcoming the move.

“I support the State Department’s announcement today regarding the need to seek additional information about the Keystone XL Pipeline proposal,” he said. “Because this permit decision could affect the health and safety of the American people as well as the environment, and because a number of concerns have been raised through a public process, we should take the time to ensure that all questions are properly addressed and all the potential impacts are properly understood.”

The $7 billion project by TransCanada, years in the making, would bring oil from the tar sands in Canada to refineries in the U.S. south. Proponents say it is key to securing more stable sources of energy.

The move avoids a politically difficult decision that was expected before the end of the year. Opponents, namely environmental advocates, warned of the carbon emissions and possible contamination risks. Supporters, including labor unions, said it would create jobs and provide secure streams of energy.

The American Petroleum Institute quickly convened a conference call with journalists, even before the official State Department announcement, declaring that any delay or denial of the project would “damage America’s energy and national security.”

Some opponents, however, cheered the decision.

“President Obama is making the right and tough decision,” said Jane Kleeb, founder of BOLD Nebraska, which organized protests against the pipeline in that state. “We hope he continues to consider climate, health and the impacts of extreme energy like tar sands on our land and water while creating a path to real energy independence. The bottom line is, when President Obama stands up to big oil, we stand with him.”

Others were optimistic, yet cautious.

“The president should know that nothing that happened today changes our position — we’re unequivocal in our opposition,” said activist Bill McKibben, founder of 350.org and another protest organizer. “If this pipeline proposal reemerges from the review process intact we will use every form of nonviolent civil disobedience to keep it from ever being built. We take courage from today’s announcement. It’s an unspoken salute to the power of people who come together in the open to demand action; it gives us some clues about how to fight going forward.”