Environmental organizations such as the Natural Resources Defense Council (NRDC) also oppose the project due to its transportation of oil from oil sands. In its March 2010 report, the NRDC stated that "the Keystone XL Pipeline undermines the U.S. commitment to a clean energy economy", instead "delivering dirty fuel at high costs". On June 23, 2010, 50 Democrats in Congress in their letter to Secretary of State Hillary Clinton warned that "building this pipeline has the potential to undermine America's clean energy future and international leadership on climate change", referencing the higher input quantity of fossil fuels necessary to take the tar and turn it into a usable fuel product in comparison to other conventionally derived fossil fuels.