The fallout from a ruptured oil pipeline in the Yellowstone River this month is spilling into a larger debate over whether the U.S. should allow the expansion of a pipeline that would carry more crude from Canada's oil sands to American refineries.

The July 1 accident at Exxon Mobil Corp.'s Silvertip pipeline has been taken up by environmentalists and other opponents of TransCanada Corp.'s planned expansion of its Keystone XL pipeline, which is not related to the Exxon pipeline. The U.S. State Department, which must approve the expansion, has said it would make a decision by year's end.