Saying "we need to be cautious" because a tar sands oil pipeline from Canada to Texas would pose " a direct threat to America's heartland," U.S. Rep. Steve Cohen (D-Tenn.) joined environmentalists Wednesday in opposing quick authorization of the Keystone XL project.

The TransCanada 1,700-mile proposed line would stretch from Alberta, Canada, through Montana, South Dakota, Nebraska, Kansas and Oklahoma and wind up on the Texas Gulf coast near Port Arthur.

Proponents say it would provide a stable source of oil that could not be disturbed by events in the Middle East or Venezuela.

Cohen, D-Tenn., joined U.S. Rep. Peter Welch, D-Vt., and representatives from the Natural Resources Defense Council and the Sierra Club on a conference call with reporters around the country. They sought to call attention to the project and the opposition expressed by 50 members of Congress.

The NRDC's executive director, Peter Lehner, said going forward with the project would show "we're acting crazy with our addiction" to oil. He noted that the project would cross a major aquifer.

Cohen and 49 other lawmakers signed a letter to Secretary of State Hillary Clinton asking her to consider whether the project is in the national interest and to require that the project be the subject of stringent environmental assessments.

"We need to be conservative. We need to protect our environment and we need to be cautious," Cohen said at Wednesday's press conference. "As oil continues to pour into the Gulf, we should take a step back and reconsider the wisdom of trusting these oil companies."

TransCanada did not respond to e-mailed and telephone requests for comment.

Copyright (c) 2010, The Commercial Appeal, Memphis, Tenn. Distributed by McClatchy-Tribune Information Services.