Today is the end of the State Department’s public comment period for environmental issues associated with the Keystone XL pipeline application, and foes of the pipeline held a conference call to mark the occasion and call on State to pay attention to climate change issues.

The Keystone XL pipeline, which President Obama rejected early this year because he said environmental issues could not be settled by a congressionally mandated deadline, would carry crude oil from Canada’s oil sands to refineries along the Gulf of Mexico coast of Texas. The pipeline owner, TransCanada, filed a new application in May.

The State Department, which is handling the permit because the pipeline would cross an international border, said it would consider a variety of issues, including air quality and noise, environmental justice, water resources, land use, recreation and socioeconomics.

Leading critics say the State Department should also weigh climate change because the extraction of crude from oil sands resembles strip mining and requires large amounts of energy. As a result, more greenhouse gas emissions are released during the extraction process than during the drilling of conventional crude oil.

“It is a tar sands pipeline that brings many risks but offers very little in the way of benefits,” said Anthony Swift, an international attorney with the Natural Resources Defense Council. “The climate emissions of this project are the equivalent of putting 4 million to 6 million more cars on the road.”

Bill McKibben, a Middlebury College professor who has led opposition among people worried about the greenhouse gas emissions, said, “The State Department has a lousy record of dealing with climate change. They struck out at Copenhagen. And they have nothing to show for their efforts regarding what is without doubt the most pressing problem the world faces.”

Supporters say that if the Keystone XL pipeline is blocked that Canada will still produce crude from its oil sands and simply send it elsewhere, to Asia for example, and that the extra emissions from tankers would be even worse for the environment. But McKibben said that building a pipeline to Canada’s west coast would also run into opposition from environmentalists and that stopping the Keystone XL would slow development of the oil sands.

Meanwhile, TransCanada said it would start construction this summer on the southern leg of the pipeline project. On Friday, it received the third and last permit it needed from the Army Corps of Engineers to build the portion of the pipeline that will run from Cushing, Okla., a major terminal and pipeline junction, to the Port Arthur area of Texas.

The company said that the environmental review completed last year “was the most comprehensive process ever for a cross border pipeline. Based on that work, TransCanada expects its cross border permit should be processed expeditiously and a decision made once a new route in Nebraska is determined. The DOS has indicated it expects to make a decision on the project by the first quarter of 2013.”