The looming shutdown would be especially troublesome for tribes that receive such essential services as police and health care directly from federal employees, said Jacqueline Johnson Pata, executive director of the National Congress of American Indians. Those tribes tend to be the most impoverished and many aren't in a position to make up for the loss of government services.
Leaders on the Fort Belknap Reservation in Montana, meanwhile, say they'll even have to halt trash pickups if lawmakers can't reach a budget agreement by Friday's midnight deadline.
During the 1995 government shutdown that lasted 21 days, all 13,500 Bureau of Indian Affairs employees were furloughed, and there were delays in general assistance payments for basic needs to 53,000 benefit recipients.
Like the last time around, however, a U.S. Department of Health and Human Services official said Indian Health Service hospitals and clinics on tribal lands would likely see little impact because their services are deemed critical.
Many tribes are still assessing likely impacts following tribal council meetings and sessions with staff held earlier in the week on how to move forward.
"There would be a significant financial impact on our daily operations and the (tribal) council would have to make some tough decisions," said Robert McDonald, a spokesman for the Confederated Salish and Kootenai tribes in Montana. "Our director of social services is very concerned about the services he could provide."
The federal government provides services directly or indirectly through contracts, grants and compacts to nearly 2 million American Indians and Alaska Natives, who have long had a unique relationship with Washington through the federal government's treaty obligations.
Officials on the Navajo Nation, the country's largest Indian reservation, said the tribe receives two-thirds of its money from the federal government to support jails, police force, social services and other programs.
The tribe said it would have enough money to run those programs for about a month but anything longer would be more difficult.
Many tribal officers on the 27,000 square-mile reservation that covers parts of Arizona, Utah and New Mexico travel hundreds of miles to respond to crimes, so law enforcement already faces a tough situation, said Sherrick Roanhorse, executive chief of staff.
"Our priority is to ensure that law enforcement and human services stay intact," he said.
It's unclear whether tribes that replace their federal funding would be reimbursed after a budget is passed. Artman, the former BIA official, said the agency's response might be that it doesn't have a process for that, it would violate rules or that the tribes don't have a right to demand a refund.
"Politically you'll understand it, emotionally you'll understand it," Artman said. "But from an accounting and regulatory perspective, it may not be possible to achieve what the tribe wants."
Tribes are hopeful law enforcement would be kept on the job as well, but BIA spokeswoman Nedra Darling declined to specify the agency's plans.
"There are things I think people are working on right now, but they're not for public consumption at this point," Darling said late Wednesday.
Darling confirmed that tribes were sent a letter advising them to draw down any money that's available from the federal government in case it shuts down. That money already has been limited because of continuing budget resolutions.
"It becomes a way of life if you're a tribe," said Robert McNichols, a former superintendent for the BIA's Truxton Canyon Agency in Arizona. "It's not anything new for them to face challenges that they don't have resources."
The impact to the 183 schools under the BIA's Bureau of Indian Education would depend on the extent to which they are supported by the federal government, said Artman.
Many of the elementary, secondary and dormitory schools are run by tribes through contracts with the federal government, and tribes could choose to supplement that funding if needed. A third that are operated directly by the BIA likely would be shut down, Artman said.
Any services from local or regional BIA offices would be curtailed, such as permitting, business site leasing or housing improvements as federal employees are sent home.
In Montana, the Confederated Salish and Kootenai tribal council recently met with department heads to go over their options if federal funding were suspended. They discussed dipping into other funds or running a skeleton crew to provide basic services to the most vulnerable residents, but no final decisions were made, McDonald said.
The Choctaw Nation of Oklahoma, meanwhile, was assuring members that all services would remain, said tribe spokeswoman Judy Allen. But she added that the Choctaws feel "it is imperative that a resolution be found soon so that federal funds ... continue to be available."
Loren "Bum" Stiffarm, chief administrative officer for the Fort Belknap Reservation, said his main concern is that a shutdown could occur as the Milk River threatens to spill over its banks. The rising river is predicted to go into flood stage within a week, and if it causes significant damage to the reservation, tribal officials will be seeking federal emergency assistance.
The reservation in northern Montana is home to the Gros Ventre and Assinboine tribes. Tribal leaders were expected to discuss the Milk River situation with the Interior Department on Thursday.
"We hope to come away with a formal assurance that they will assist us if the flooding occurs," Stiffarm said.
Fort Belknap plans to have only essential staff working if there is a government shutdown. Some programs and services would be put on hold, including garbage pickup, but the tribal government will continue to provide for the welfare of the people, he said.
Associated Press writers Matt Volz in Helena, Sudhin Thanawala in San Francisco, Shannon Dininny in Yakima, Wash., and Murray Evans in Oklahoma City contributed to this report.