Such a vote may be symbolic, highlighting Ms. Landrieu’s support for the pipeline and her influence on energy issues in Washington - a centrepiece of her campaign. Democratic leaders may have trouble mustering the votes for passage, and President Barack Obama could veto the measure.

Ms. Landrieu said she was “confident that we have the additional votes necessary to pass it.”

Ms. Landrieu spoke Wednesday as Congress convened for a lame-duck session after Republicans won control of the Senate in the Nov. 4 election. Republicans picked up eight seats thus far, while her race goes to a runoff because neither she nor Cassidy, 57, won a majority.

Senator Richard Durbin of Illinois, the chamber’s second- ranking Democrat, Wednesday said party leaders were discussing trying to schedule a Keystone vote to aid Landrieu.

“It’s obviously an important issue to her, and it has importance in terms of timing with her runoff coming up,” Mr. Durbin said. “What she’s trying to do is find an opportunity to bring this up publicly in the closing weeks of the session.”

Ms. Landrieu, 58, chairwoman of the Energy and Natural Resources Committee, in her campaign has sought to distance herself from Mr. Obama on energy issues, including his delay in approving the pipeline.

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