A U.S. government study showed on Friday that the proposed Keystone XL oil pipeline would not significantly increase carbon emissions, clearing a key hurdle to move forward the long-delayed project. "Approval or denial of any one crude oil transport project, including the proposed project, is unlikely to significantly impact the rate of extraction in the oil sands or the continued demand for heavy crude oil at refineries in the United States based on expected oil prices, oil-sands supply costs, transport costs, and supply-demand scenarios," the U.S. State of Department said in its final environmental impact review for the Keystone XL project. The 7-billion-U.S. dollar Keystone XL pipeline, proposed by Canada's No. 2 pipeline company TransCanada more than five years ago, would run 1,700 miles (2,720 km) to connect Canada's oil sands to refineries around Houston and the Gulf of Mexico. To cross the U.S.-Canadian border, it needs a permit by U.S. President Barack Obama. The project has been delayed for years as critics say it could worsen climate change by enabling further growth from the oil sands, which create higher greenhouse gas emissions than some other forms of production. Obama has also said he wouldn't approve Keystone XL if it would exacerbate carbon pollution. The study did not recommend whether Obama should approve or deny the proposed pipeline. There's now a 90-day period for the State Department to make its decision on whether the project is in the U.S. national interest. "The President Permit review now focuses on whether the proposed project serves the national interest", which involves consideration of energy security, economic policy, foreign policy and other factors, said the department. Republicans and oil industry groups welcomed the study and urged Obama to approve the pipeline. "This report from the Obama administration once again confirms that there is no reason for the White House to continue stalling construction of the Keystone XL Pipeline," U.S. Senate Republican leader Mitch McConnell said in a statement.