SIOUX FALLS (AP) – South Dakota Gov. Kristi Noem appeared headed Monday for a legal confrontation with two Native American Indian tribes over highway checkpoints intended to keep the coronavirus away from their reservations.

The issue pits an ambitious governor who has taken a mostly hands-off approach to restrictions on daily life during the pandemic against tribes who say her actions jeopardize their members. And it's the latest flare-up in a relationship that has been tense since Noem took office in 2018, most notably in a longstanding conflict over construction of the Keystone XL pipeline.

The Cheyenne River Sioux, in northern South Dakota, and the Oglala Lakota Sioux, in the southwest corner of the state, began their roadblocks in April. Both tribes cited the threat of the virus, combined with their vulnerable populations and poor medical facilities, as urgent reasons to control access.

On Friday, Noem gave the tribes 48 hours to dismantle the checkpoints and said the state would sue if they didn't. Both tribes said over the weekend the checkpoints would stand on their reservations, which range from 3,500 to 4,000 square miles in size — larger than some states.

“We will not apologize for being an island of safety in a sea of uncertainty and death,” Cheyenne River Sioux chairman Harold Frazier said in a statement.

He described a health care system on the reservation with eight hospital beds and six ventilators, saying that the infection could “spread like wildfire” if they weren't vigilant.

The tribes say they are still allowing essential businesses onto the reservations and said the checkpoints were set up to keep out tourists or other visitors who could be carrying coronavirus infections. The reservations are collectively home to about 30,000 people.

Oglala Sioux president Julian Bear Runner called the state's approach to the coronavirus pandemic “ineffective,” pointing to a spike in confirmed cases in the state after a mass testing event last week at a hot spot.

The Bureau of Indian Affairs sent a memo to tribes last month saying that they could restrict access to roads on tribal land only after they had consulted and reached an agreement with whoever owns the road. At least one other tribe, the Crow Nation of Montana, set up roadblocks to control reservation access amid coronavirus fears. Those have caused no issues with the state since they began in late March.

The South Dakota tribes said they discussed the plan with state officials last month and didn't receive objections from the governor's office until Friday. They said they are allowing essential traffic through the highways that cross the reservation.

Noem disputes that. She said the required consultation and agreements never happened, and she's been getting complaints from travelers, business, ranchers and state agencies that they are having difficulty passing the checkpoints. She said she had been talking with the tribes for weeks in hopes of resolving the issue.

“We need to continue to see those essential services move through the checkpoints,” Noem said. “We need to be able to get ranchers to their cattle, people to their property, and to make sure that we’re allowing people who want to travel through the area to continue to do so and not to be stopped and turned around.”

The governor said she hoped she could reach a resolution with the tribes, but also said she didn't think the checkpoints on state and federal highways were a “good idea.” She didn't give any update Monday on the timing of any legal action.

Nathan Sanderson, president of the South Dakota Retailers Association, said he reached out to the governor's office after several stores in and around the Cheyenne River Reservation said they were having a hard time getting deliveries because of the checkpoints.

Sanderson said he wasn't aware of any deliveries being turned around at the checkpoints, but said they had caused some companies to stop making deliveries to the stores.

Noem's uncomfortable relationship with tribes dates to her first year in office, in 2018. Noem, mindful of the tumultuous, costly and sometimes violent demonstrations in neighboring North Dakota over the Dakota Access pipeline, pushed the Legislature to pass laws that heightened penalties for violent protest against the Keystone XL pipeline.

Though portions of the laws were tossed out by a court, Noem successfully pushed through modified versions earlier this year.

Pending construction on the Keystone XL in coming months may be one reason the roadblocks are becoming an issue. The highways that the Cheyenne River Sioux Tribe are monitoring connect to several potential construction sites of the proposed pipeline route, which skirts tribal lands. Noem's office didn't immediately respond to a question of whether the Keystone project is a factor.

Remí Bald Eagle, a spokesman for the tribe, said it has a policy of not allowing vehicles from any oil company on the reservation and with the checkpoints set up, they would stop those vehicles.

Bear Runner, the Oglala Sioux leader, asked Noem in an April 23 letter to block Keystone construction during the pandemic.

State Sen. Troy Heinert, a Democrat from Mission, said Noem's ultimatum threatens to worsen the state's relationship with tribes.

Several lawmakers who represent Native American communities wrote to Noem over the weekend criticizing her ultimatum and saying they could have set up a conversation that took into account the history, culture and protocols for working with tribal governments.

“Everybody's on edge already and this does not help,” Heinert said.