A group of 68 lawmakers asked Secretary of the Interior Sally Jewell to exclude two portions of the Alaskan Arctic Ocean from all future oil and gas lease sales.

Led by California Democrat Rep. Jared Huffman, the lawmakers asked Jewell to keep the Chukchi and Beaufort seas from future leasing. The two Alaskan areas have been approved for drilling by the Obama administration.

In their letter, the lawmakers argue that not drilling in the Arctic Ocean is one of the only ways the United States can help meet the Paris Agreement's target of keeping global temperature rise below 2 degrees Celsius. Most scientists blame greenhouse gas emissions from burning fossil fuels, such as crude oil and coal, for driving manmade global warming.

"Scientific consensus tells us that the vast majority of known fossil fuel reserves must be left undeveloped if we are to avoid the worst effects of climate change," the letter stated, "and the development of Arctic Ocean oil and gas has specifically been identified as incompatible with the president's commitment to keep the planet's average temperature rise under 2 degrees Celsius."

Sixty-seven Democrats and one Republican, Rep. Robert Dold of Illinois, signed the letter. A number of environmentalist organizations also joined the effort, including the Sierra Club, the Alaska Wilderness League, the Wilderness Society, Earthjustice, the League of Conservation Voters and the Natural Resources Defense Council, among others.

The Interior Department estimates the Chukchi Sea holds 15 billion barrels of recoverable oil and 78 trillion cubic feet of recoverable natural gas. The Beaufort Sea could hold 8 billion barrels of oil and nearly 28 trillion cubic feet of natural gas.

The Chukchi Sea was targeted by Shell for drilling last year, but the Dutch company pulled out after disappointing initial returns from wells drilled in the area. Statoil, a Norwegian company, also planned to drill in the Chukchi Sea, but decided to stop operations in the Arctic in November 2015.

The falling price of oil is generally cited as the main reason for oil companies deciding to step away from drilling in the Arctic Ocean, but regulatory hoops set out by the Obama administration also have been cited as a possible cause.

The letter from the lawmakers said it was time for the administration to get even tougher, and that means keeping all fossil fuels underneath the Arctic.

"Ending oil and gas development in the Arctic would send a powerful international signal that the United States is committed to investing its resources in a climate safe, clean-energy future," the letter stated.