John M. Broder / New York Times News Service

WASHINGTON — The State Department issued a revised environmental impact statement for the 1,700-mile Keystone XL pipeline Friday, which makes no recommendation about whether the project should be built but presents no conclusive environmental reason it should not be.

The lengthy document also draws no conclusions on whether the pipeline is in the United States’ economic and energy interests, a determination to be made later this year by President Barack Obama. But it will certainly add a new element to the already robust climate change and energy debate around the $7 billion proposed project.

The study will help guide the president’s decision, but it does not make the politics any easier. Environmental advocates and landowners along the route have mounted noisy protests against the project — including a large demonstration in Washington last month — and view Keystone as a test of Obama’s seriousness about addressing global warming.

The president faces equally strong pressure from industry, the Canadian government, many Republicans and some Democrats in Congress, local officials and union leaders, who say the project will create thousands of jobs and provide a secure source of oil that will replace crude from Venezuela, Saudi Arabia and other potentially hostile suppliers.

The draft report, which updates a 2011 study that essentially gave the project a green light, weighs the impact of the pipeline, which would carry about 800,000 barrels a day of heavy crude oil from tar sands formations in Alberta across the Great Plains to Gulf Coast refineries.

The new impact statement says that extracting, shipping, refining and burning oil from the tar sands produces more climate-altering greenhouse gases than most conventional oil but less than many of the project’s critics claim. The State Department study says that tar sands oil produces 5 percent to 19 percent more greenhouse gas emissions than other crude, depending on what oil was compared and who performed the calculations.

It says that Canada and its oil industry partners will probably continue to develop the oil sands even if the Keystone XL pipeline is not built. It states that building or not building the pipeline will have no significant impact on demand for heavy crude in the United States.

Publication of the document next week starts a 45-day public comment period and then a protracted review before a final impact statement is issued, meaning a presidential decision on the project is still months away.