White House spokesman Jay Carney today emphasized the obstacles facing environmentalists who hope to force a presidential veto of the $7 billion Canada-to-U.S. oil pipeline known as Keystone XL, depicting the project's fate as resting with the State Department. Carney walled off President Obama from the mushrooming controversy over the 1,700-mile pipeline -- which would nearly double U.S. imports of emissions-intensive Canadian oil-sands crude if approved by State -- six days before green groups plan a massive White House protest aimed at prodding the president to personally nix the XL link.