Native American tribes and environmental groups pressured a U.S. federal judge on Thursday to shut down work on the disputed Keystone XL pipeline from Canada to Nebraska, citing fears workers could spread the coronavirus and construction could damage land.

After years of delays, the company is rushing ahead amid the pandemic to get part of the line built so it will be harder to stop, attorneys for the project's opponents argued in a teleconference to decide if the construction should be halted.

They warned that plans to build construction camps housing up to 1,000 workers each pose a risk to tribes and rural communities that already struggle to provide basic health-care services and would face challenges responding to coronavirus outbreaks.

Construction was finally supposed to start this spring following a major investment by the Alberta government.

The first U.S. segment of the 1,900-kilometre oilsands pipeline was installed by Calgary-based TC Energy this week across the border in northern Montana.

The fight over the line stretches back more than a decade after it became a lightning rod in the debate over fossil fuels' contribution to climate change.

"With the rise of the pandemic, it is even more important to protect the tribe to at least put a pause on this activity, take a hard look at this," said Matthew Campbell, an attorney for the Native American Rights Fund representing the Rosebud Sioux Tribe of South Dakota and the Assiniboine and Gros Ventre tribes of the Fort Belknap reservation in Montana.

President Donald Trump is a champion of the $8-billion project and gave it a presidential authorization in a bid to circumvent a 2018 court ruling that had blocked it.

The same judge who made that ruling, U.S. District Judge Brian Morris in the Montana city of Great Falls, presided over Thursday's hearing, which also included arguments over whether Trump's authorization was legal.

Ruling against new permit

Late Wednesday, Morris handed another setback to TC Energy with a ruling that invalidated a key U.S. Army Corps of Engineers clean water permit. The so-called nationwide permit applied to a broad range of projects including Keystone XL, and is needed to so the pipeline can cross rivers, streams and other waterways.

Northern Plains Resource Council and other activist groups challenged the Corps' re-issuance of a nationwide permit in 2017.

Such permits are a means of streamlining the permitting process for certain projects, although the Army Corps can also issue permits case by case. Nationwide Permit 12, which governs projects such as pipelines and utility lines, must be reissued every five years or left to expire.

Morris ruled that the Corps violated federal law by failing to adequately consult on risks to endangered species and habitat, and it must comply before it can apply the nationwide permit to any project.

The ruling does not affect current work on a span of the $11-billion Keystone XL pipeline across the Canada-U.S. border, but it does raise questions about securing water-crossing permissions for the rest of the route, said Jared Margolis, senior attorney with the Center for Biological Diversity, one of the plaintiffs.

Alberta Premier Jason Kenney announced last month that the provincial government would provide the Keystone XL pipeline with an investment of $1.5 billion, plus a $6-billion loan guarantee. (Todd Korol/The Canadian Press)

"Most of the rest of the project has water crossings everywhere [so] it does affect construction overall," Margolis said. "They can't move forward now on huge chunks of the project."

The U.S. Army Corps could not be immediately reached.

TC Energy is reviewing the ruling, said Terry Cunha, spokesman for the Calgary-based company.

"As we determine our next course of action, we will continue with our construction activities currently underway at the border crossing as the ruling doesn't impact our current activities in any way," Cunha said in a statement Thursday.

"We remain completely committed to the Keystone XL project."

Cunha added that while the judge's ruling is "disappointing" in relation to Keystone XL, the impacts of his ruling are broad-reaching and could have implications far beyond the one project.

"The ruling directly impacts various utilities constructing and maintaining infrastructure projects, including natural gas, liquids, television cable, electrical transmission, telephone, internet, among others," he said.

"This decision hampers their ability to build or maintain infrastructure projects that cross wetlands or waterbodies across the U.S."

Alberta in March said it would invest $1.5 billion in Keystone XL, plus provide a $6-billion loan guarantee, to get the project built.

Kavi Bal, a spokesperson for Alberta Energy Minister Sonya Savage, reiterated the government's commitment to the project in a statement to CBC News.

"A Montana judge ruled on a very narrow and specific decision asking the United States Army Corps of Engineers to conduct additional review regarding two specific Keystone XL pipeline river crossings," he said.

"Keystone XL has had a significant amount of anti-energy activist opposition in the past and this challenge is not surprising. We cannot surrender development to those who seek to kill projects with endless court challenges."

The Keystone XL pipeline has faced loud opposition for several years, including this protest in Washington, DC, in 2014. (Nicholas Kamm/AFP/Getty Images)

Bal said the province remains "committed to this extremely important project."