The U.S. government expects to make a decision on a permit for an extension to the Keystone pipeline from Canada by the end of the year, an official said. Canadian pipeline company TransCanada wants to build Keystone XL to supplement its existing pipeline carrying tar sands oil from Alberta. The current network terminates in Oklahoma and Illinois and the extension would end along the Gulf of Mexico. The U.S. State Department needs to approve the project because the pipeline crosses the Canadian border.U.S. Secretary of State Hillary Clinton said during a news conference with Canadian Foreign Affairs Minister John Baird that her government was reviewing \"hundreds of thousands of comments\" on the pipeline proposal.\"We are leaving no stone unturned in this process and we expect to make a decision on the permit before the end of this year,\" she said.Keystone XL would send roughly 15 million barrels of oil to the United States every month. Critics of the project point to the number of spills on the existing Keystone oil pipeline and the potential environmental impact of heavy crude oil from tar sands projects in Alberta. Baird said the pipeline proposal would be important for the future of the Canadian economy. \"It is a very important project not just for our government, but I think for Canadians and the future of the Canadian economy,\" he said.