According to National Parks, the president is finalizing a settlement with lawyers from the snowmobile industry that would bring snowmobiles back into the Yellowstone, hampering the National Parks Service decision to phase out snowmobile traffic.

The organization said that the senator's letter urges the president to "eliminate the serious impacts from tens of thousands of individual snowmobiles entering the park."

"In Yellowstone, elk, buffalo, and other wildlife are often forced out of their habitat by hundreds of snowmobiles racing through the park each hour," according to a National Parks written statement. "Snowmobile traffic puts stress on the park's wildlife during a winter season that is often difficult for the animals to survive."

The Park Service said its decision to phase out the use of snowmobiles was a result of 13 years of scientific study complemented with a three year public survey in which "tens of thousands" of citizens responded.

According to the Park Service, the study revealed that visitors to Yellowstone, as well as rangers, have suffered headaches, nausea, watering eyes and sore throats from breathing snowmobile exhaust. They also complained that the roar and the splash of the snowmobiles routinely drowns out "the hiss and splash of Old Faithful geyser."

The senator's letter was endorsed by the National Parks Conversation, Greater Yellowstone Coalition, Bluewater Network and The Wilderness Society and notes: "These public comments endorsed the Park's Service's decision to provide winter vehicular access to Yellowstone in a way that does not damage resources or conflict with the enjoyment of other visitors."

The eleven senators were, Harry Reid (Democrat) of Nevada, Lincoln Chaffe (Republican) of Rhode Island, Debbie Stabenow of Michigan, Paul Sarbanes of Maryland, Bob Graham of Florid, Maria Cantwell of Washington, Barbara Boxer of California, Jack Reed of Rhode Island, Jon Corzine of New Jersey, John Kerry of Massachusetts, and Joseph Lieberman of Connecticut.

"Throughout the country, citizens are making it clear that they want laws upheld and their environment protected," Kevin Collins, of the National Parks Conservation Association, said. "These senators have sent a strong reminder to the White House that Americans have been especially clear about their desire to see Yellowstone National Park fully protected."