Keystone XL Debate Pits Environmentalists Against Unions

On Sunday, thousands of protesters are expected to lock arms outside the White House and try to influence President Obama's decision on Keystone XL, the proposed, 1,700-mile oil pipeline that would stretch from Alberta, Canada, through U.S. mountain and plains states, to the Texas Gulf Coast.

This week, the president said that while the State Department is reviewing the decision, he alone will make it and no matter the outcome, it will likely divide the president's base.

Unions are fighting for the pipeline, which they say will provide 20,000 jobs. Environmentalists oppose it because of potential oil spills and the greenhouse gases they say the process would cause.