The State Department released a draft environmental impact assessment of the controversial Keystone XL pipeline Friday, suggesting that the project would have little impact on climate change.

Canada’s oil sands will be developed even if President Obama denies a permit to the pipeline connecting the region to Gulf Coast refineries, the analysis said. Such a move also would not alter U.S. oil consumption, the report added.

The lengthy assessment did not give environmentalists the answer they had hoped for in the debate over the project’s climate impact. Opponents say a presidential rejection of the project would send a powerful message to the world about the importance of moving away from fossil fuels and make it more difficult for Canada to export its energy-intensive oil.

But the detailed environmental report — almost 2,000 pages long — also questions one of the strongest arguments for the pipeline, by suggesting that America can meet its energy needs without it. The growth in rail transport of oil from western Canada and the Bakken formation on the Great Plains and other pipelines, the analysis says, could meet the country’s energy needs for the next decade, even if Keystone XL is never built.

In a news conference Friday, Kerri-Ann Jones, assistant secretary of state for oceans and international environmental and scientific affairs, said the department had not made any final conclusions about the project. “We feel that we need to have a public debate,” Jones said.

The president is not likely to make a decision on TransCanada’s permit application until midsummer at the earliest. The analysis will be subject to at least 45 days of public comment once it is published next week in the Federal Register, and the State Department will have to respond to hundreds of thousands of comments before finalizing its environmental impact statement. The State Department will also have to conduct a separate analysis of whether the project is in the national interest, a question on which eight other agencies will offer input over 90 days.

Jim Lyon, vice president for conservation policy at the National Wildlife Federation, said the department’s analysis “fails in its review of climate impacts, threats to endangered wildlife like whooping cranes and woodland caribou, and the concerns of tribal communities.”

By rejecting the project, Lyon added, “President Obama can keep billions of tons of climate-disrupting carbon pollution locked safely in the ground. . . . Without access to major U.S. export terminals from Keystone XL and other routes, tar sands production will be substantially slowed.”

The report’s executive summary takes a different view, saying it “concludes that approval or denial of the proposed Project is unlikely to have a substantial impact on the rate of development in the oil sands, or on the amount of heavy crude oil refined in the Gulf Coast area.”

Supporters of the project say it will ensure a secure supply of oil from Canada, one of the nation’s closest allies, and will generate high-paying U.S. jobs over the project’s two-year construction.

“With unemployment in construction still over 16 percent and cuts to public construction funding beginning today with sequestration, private projects like Keystone XL create jobs that operating engineers are waiting to perform as they seek to put food on the table and pay the mortgage,” International Union of Operating Engineers General President James T. Callahan said.

American Petroleum Institute spokeswoman Sabrina Fang said the pipeline will not just generate jobs but “is also going to help reduce our dependence on oil from less stable parts of the world.”

Canada’s ambassador to the United States, Gary Doer, said he and other Canadian officials are “going to use the common sense that’s in this report” to press their case for the pipeline, even though they will remain respectful of America’s “democratic process.”

The United States imports 866,000 barrels of oil a day from Venezuela, Doer said. “Why not get those 866,000 barrels a day from Alberta, Montana and North Dakota?” he asked.

The Keystone XL has sparked opposition along the pipeline route, where it crosses rivers, ranches and farms, and across the country, where critics said it would facilitate the exploitation of Canada’s oil sands, or tar sands. Because the extraction of bitumen from those sands is an energy-intensive process, it emits more greenhouse gases than the extraction of oil from conventional reservoirs.

Calgary-based pipeline company TransCanada first applied for a permit in September 2008. In February 2012, Obama postponed a ruling, citing the pipeline’s path through more than 90 miles of the ecologically sensitive Sand Hills region of Nebraska, and said he would consider a revised application.

In March, Obama embraced the southern leg of the project, which would extend from Cushing, Okla., to Texas. By late summer, the Army Corps of Engineers had issued permits, and TransCanada chief executive Russ Girling recently said that 45 percent of the construction of that leg was complete. Pipeline foes turned to civil disobedience, camping out on platforms hoisted into trees in the pipeline’s path.

TransCanada filed a new application in May for the northern leg, pushing the route further east in Nebraska, avoiding all but 10 miles of sensitive areas.

The northern leg would run from Hardisty, Alberta, to Steele City in southern Nebraska. An existing pipeline would connect the two legs.