A Senate vote to approve the controversial Keystone Pipeline may not happen this week as planned.
The measure already appeared unlikely to pass.
Now it's tangled up in a dispute between Democrats and Republicans over a separate energy efficiency bill.
Senate Majority Leader Harry Reid warned Republicans they would only get a vote on Keystone if they don't block the energy efficiency measure.
Republicans threatened to do just that if they don't get to add amendments to the energy efficiency bill.
The Keystone Oil Pipeline has been on hold with environmentalists opposed to the project, while supporters say it'll bring jobs to the U.S..
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