The US State Department on Friday released a long-awaited review of a controversial pipeline project to bring oil from Canada to Texas, concluding it would have little impact on climate change or the environment.

The final environmental impact assessment could now pave the way for US President Barack Obama to approve the $5.3 billion, 1,179-mile (1,897-kilometer) Keystone XL pipeline, first proposed back in 2008.

The project has pitched environmental groups against the oil industry, which has argued that it will bring much-needed jobs to the United States and help fulfill the US goal of energy self-sufficiency.

The 11-volume highly technical report released Friday stopped short of making a recommendation. US officials stressed it was meant to help inform the final decision, rather than lean in one direction or another.

But it raised no major objections to the plan, and said building and using the pipeline would not in itself significantly increase greenhouse gases, blamed for climate change.

"The analyses of potential impacts associated with construction and normal operation of the proposed project suggest that significant impacts to most resources are not expected along the proposed project route," the huge report said.

"Approval or denial of any one crude oil transport project, including the proposed project, remains 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."

Canadian Natural Resources Minister Joe Oliver said he was "encouraged" by the report's conclusions, recalling that the project had now undergone a lengthy review process.

"The benefits to the United States and Canada are clear. We await a timely decision on this project," he said.

The Keystone XL project aims to carry some 830,000 barrels of heavy crude a day from Alberta's oil sands south to Nebraska refineries before joining an existing pipeline to be shipped to Texas.

The United States has to approve some 875 miles (1,400 kilometers) of the new route which would cross American territory.

But it has been long delayed amid concerns it could damage sensitive wetlands and endangered species in Nebraska and South Dakota.

The Natural Resources Defense Council argued the report in fact acknowledged the risks.

"Piping the dirtiest oil on the planet through the heart of America would endanger our farms, our communities, our fresh water and our climate," said international program director Susan Casey-Lefowitz.

But the State Department insisted oil giant TransCanada, which operates oil and gas pipelines in North America, has pledged to comply with all laws and regulations.

Environmental damage would be limited, providing that "Keystone would incorporate the mitigation measures that are required in permits issued by environmental permitting agencies into the construction, operation, and maintenance of the proposed project."

More than 1.9 million comments to the draft impact assessment have been sifted through to arrive at the final report. There will now be a 90-day consultation for all government agencies to review whether the pipeline is in the national interest.

"Our national interest will be served only if this project does not significantly exacerbate the problem of carbon pollution," Obama said in a speech in June.

Republican US lawmakers have lined up to call on the Obama administration to approve the project.

House Speaker John Boehner, who claims the project would create some 100,000 jobs, said allowing the decision to languish was "economic malpractice" and declared: "President Obama is out of excuses."

"Mr President, no more stalling, no more excuses. Please pick up that pen you've been talking so much about and make this happen. Americans need these jobs," added Senate Republican Minority Leader Mitch McConnell in a statement.