A State Department draft environmental impact statement, any environmental effects from the development of tar sands would likely occur with or without Keystone XL. The review said rail deliveries should be considered when weighing the project's national interest, however.
A meeting is scheduled for April 18 in Grand Island, Neb., to provide the public with an opportunity to address the impact statement.
Nebraskans' concerns about the environmental effects of the pipeline led planner TransCanada to reroute the project before it received state government approval.
Congressional leaders have tried to pressure the federal government to sign off on the pipeline. Keystone XL requires presidential approval as a cross-border project.
Supporters say the pipeline is needed for North American energy security and economic stimulus. Detractors have expressed concern about the potential environmental impacts.
"Tar sands crude is the most dangerous oil on earth," Michael Marx, director of the Sierra Club's Beyond Oil campaign, said in a statement. "Not only is it accountable for significantly greater carbon pollution emissions than conventional oil, which will destroy our climate, it is also highly corrosive and toxic, so when pipelines rupture it is nearly impossible to clean up."