By Kevin O'Hanlon and Valerie Volcovici

LINCOLN, Nebraska/WASHINGTON (Reuters) - Opponents of TransCanada's Keystone XL pipeline have launched a last-minute public relations blitz before Nebraska regulators weigh in on its route next week in the last big regulatory hurdle for the long-delayed project.

The proposed 1,179-mile (1,897 km) pipeline would link Canada’s Alberta oil sands to U.S. refineries. It has long been a lightning rod of controversy for environmental groups and worried about spills and global warming, and former President Barack Obama rejected it. But President Donald Trump backs it as part of his broad energy strategy, and says it will lower fuel prices, shore up national security and bring jobs.

Volunteers for Bold Alliance, an activist group that has been fighting the project since it was proposed nearly a decade ago, are knocking on doors in parts of the state to describe the threats that possible pipeline leaks could pose to groundwater.

"We want to make sure our fellow Nebraskans know the decision is coming ... and how critical this decision is for property rights and clean water," said Jane Kleeb, the group’s director, adding she has targeted districts represented by the five members of Nebraska Public Service Commission who will decide on the route.

TransCanada has said the pipeline will create jobs and public revenues, and can be operated safely.

The public service commission said it will announce its decision on the route on Nov. 20. It is charged with weighing whether the project is in the public interest of Nebraskans, but is barred from considering environmental issues because the pipeline already has an environmental permit.

During hearings on the line in August, opponents argued that there was little commercial interest in the line, given the surge in U.S. drilling over the past decade that has created a supply glut and driven down crude oil prices.

Led by 90 landowners whose farms lie along the proposed route, opponents said tax revenue from the project will be short-lived, jobs will be temporary, and a foreign company should not be allowed to use eminent domain to seize American farmland.

TransCanada has said it has received adequate support to make the pipeline viable. But the company has yet to announce results of its Keystone XL open season to gauge interest among shippers, which closed at the end of October.

"They have put out positive messaging around it so there's some level of optimism," said Wood Mackenzie analyst Mark Oberstoetter.

The Nebraska Chamber of Commerce says Keystone XL will generate an estimated $150 million in new property tax revenue for Nebraska, and expand Nebraskans’ personal incomes by more than $300 million during construction.

The Obama administration considered the line for years before rejecting it in 2015 on environmental grounds. Trump reversed that decision swiftly after taking office, which placed the final permitting decision in the hands of Nebraska. It will be the last of three states to make a decision on the pipeline's proposed route.

Lawyer Brian Jorde, who represents landowners who oppose the line, said regardless of what Nebraska regulators decide, the pipeline will not be built soon: a decision can be appealed up to 30 days after the vote in the district court, and subsequent legal challenges can take up to two years, he said.

(Additional reporting by Nia Williams in Calgary; Editing by Richard Valdmanis and David Gregorio)