WASHINGTON — Ten Nobel Peace Prize winners from as far afield as Yemen, South Africa and Argentina have signed a letter asking U.S. President Barack Obama to deny a permit for the Keystone XL pipeline that would transport oilsands bitumen to Texas Gulf Coast refineries.

The laureates, who include former U.S. president Jimmy Carter and Archbishop Desmond Tutu of South Africa, argue that denial of a permit would send a strong signal to the world that the U.S. is rejecting a fossil fuels future.

“Let this reflect the growing urgency we feel for the hundreds of millions of people globally whose lives and livelihoods are being threatened and lost as a result of the changing climate and environmental damage caused by our dangerous addiction to oil,” the letter says.

Rejection of the pipeline would set “a powerful precedent” and “would signal a new course for the world’s largest economy,” the letter says.

“History will reflect on this moment and it will be clear to our children and grandchildren if you made the right choice.”

The letter underscores Obama’s dilemma: By allowing the assessment process to take so long, he has awakened both national and international interest in a project that normally would garner only passing concern.

Now he walks a tightrope that divides his own party. With midterm elections in November, no matter what his final decision, the damage could be significant. While denial of the pipeline likely would inspire his youth base to get out the vote, it could also lose him seats the Democrats need to maintain control of the Senate.

Eleven Senate Democrats sent Obama a letter last week urging him to approve the pipeline by May 31. One of those was Louisiana Democrat and chairman of the Senate energy committee Mary Landrieu. Polls show she is running a tight race against Republican Bill Cassidy. She’s already on the defensive over the Affordable Care Act. Americans for Prosperity, the foundation financed by the oil billionaires David and Charles Koch, has spent more than $3 million since January on ads bashing her support for Obamacare.

Although Landrieu has claimed Keystone won’t decide her political future, Louisiana is an oil state and denying the pipeline could dash her fortunes.

The 30-day period of public response to the State Department’s environmental assessment finding ended March 7 with 124,989 comments.

Typical of the pipeline opposition is the comment from Roger Clark. “My position is that if Canada insists on extracting this crude then it should be Canada’s problem in terms of how to refine it and how to bring it to market,” he writes.

Many opponents challenged Secretary of State John Kerry to live up to a statement he made in 2007: “If we can put an end to the era of dirty fossil fuels, we can begin an era of sustainability — environmental, economic, and political — for our nation and the world.”

Opponent Jack Spallino said, “In America, the land of the free big oil sociopaths, we fail to come to grips with the fact that filthy Shale tars add to climate change!”

Steven Pope typically reflected proponents when he wrote: “We need jobs and we need energy independence. The Keystone XL pipeline will help us support both.”

Thousands of other proponents signed a form letter simply asking Obama to approve the pipeline as soon as possible.

The State Department’s environmental assessment concludes that Keystone would not lead to a significant increases in carbon emissions.

The review process is now in the final stages of gathering comments from eight agencies — Defence, Justice, Commerce, Interior, Transportation, Energy, Homeland Security and the Environment — to assess whether the project serves the U.S. national interest. After that, Kerry will make his recommendation to the Obama, who will make the final decision. That could come as early as June 1 or as late Obama wants to make it.

wmarsden@postmedia.com