In a tersely-worded letter signed by 350.org, Greenpeace, Friends of the Earth, NRDC, Sierra Club, and twenty other well-known green groups, the signers welcomed the idea of Canada finding new ways to reduce its growing rate of carbon pollution, but were direct in saying that making promises of future reductions the basis of a deal for the Keystone pipeline would ignite a serious backlash.

"On behalf of our millions of members and supporters nationwide," reads the letter, "we oppose any deal-making in return for the Keystone XL tar sands pipeline. Our rationale is simple. Building Keystone XL will expand production in the tar sands, and that reality is not compatible with serious efforts to battle climate change."