A measure inserted in a bill to extend payroll tax benefits gave Obama about two months to determine whether the proposed Keystone XL was in the national interest.
Nebraskans had protested the original route for the tar sands pipeline from Canada would pass over a key aquifer. That triggered the U.S. State Department to re-examine the route for the trans-national pipeline, meaning a decision wasn't likely until after November 2012 presidential elections.
Republicans said the project is "shovel ready," playing off Obama's "We Can't Wait" campaign to pressure him to approve the project. The State Department, however, said the time limit was insufficient.
Susan Casey-Lefkowitz, director of international programs at the Natural Resources Defense Council, told Washington publication The Hill the Obama administration doesn't have room to maneuver.
"The president is going to have no choice but to reject the pipeline," she said.
This, she notes, could play well for Obama's environmental base in the run-up to 2012 elections. Environmental groups say tar sands oil is bad business, pointing to a tar sands oil spill in Michigan that's taken more than a year to clean up.
"It seems like (Republicans) wrote themselves into a corner (with the tax bill)," said Sierra Club spokesman Eddie Scher.