(Maria Gallucci, InsideClimate News )

In a last action against the Keystone XL before the year ends, more than 200 U.S. and Canadian celebrities, authors, diplomats, business leaders and philanthropists sent President Obama a letter Monday urging him to reject the Alberta-to-Texas tar sands pipeline and help stop "making the climate crisis worse."

The signatories include actors Marissa Tomei and Blythe Danner, cleantech entrepreneur Vinod Khosla, Obama fundraiser and Esprit founder Susie Tompkins Buell—as well as Canadian author Margaret Atwood and Stephen Lewis, a former Canadian ambassador to the United Nations.