BOZEMAN -- Montana and federal officials announced a deal Thursday to let some bison migrate through a private ranch bordering Yellowstone National Park.

It would allow a small number of the animals to avoid slaughter under a disease control program that has claimed more than 3,000 bison since 2000.

Gov. Brian Schweitzer and park Superintendent Suzanne Lewis said the ranch's owners, the Church Universal and Triumphant, agreed to sell their grazing rights and initially allow 25 bison to pass through the property. The deal, estimated at $2.8 million, would let the bison access more than 5,000 acres of federal land outside the park.

Despite criticism from both the livestock industry and bison advocates, Lewis characterized the deal as breaking an eight-year impasse on one of the National Park Service's most divisive wildlife issues.

"Until today, bison were never allowed to use that space," she said.

All other bison leaving the park during the winter migration still would be subject to slaughter. Since last fall, a record 1,601 bison have been killed to prevent the spread of the disease brucellosis, which can cause cows to abort their calves.

Bison advocates noted most of the killings would still have occurred even if the deal had been in place, since only a small number of bison would have been allowed through the ranch.

"Sixteen hundred dead American buffalo later, they give us this lip service," said Stephany Seay with the activist group Buffalo Field Campaign. "This will do nothing to stop the slaughter and just means 25 wild bison will be run through the typical gauntlet."

Livestock industry representatives also weighed in against the deal, saying it did not directly address the core problem of brucellosis. Errol Rice with the Montana Stockgrowers Association said the park service needed to put more effort into a vaccine.

But Schweitzer said the deal was the best option on an issue that has vexed the state and the Park Service for more than a decade. He added that it removed the possibility of a brucellosis transmission to the 150 cow-calf pairs the church had owned at the Royal Teton Ranch.

"For every person in the region concerned about the bison, there are those in the cattle industry who think we're too easy on them," the governor said.

The grazing rights deal had been delayed for almost a decade. It comes on the heels of a highly critical congressional report that said state and federal agencies were largely failing in efforts to expand where bison can roam.

Beginning in 1998, the federal government paid $13 million to the church for land and conservation easements. But it was unable to seal an agreement on grazing rights, which had been delayed since 2000 as negotiations stalled and government agencies could not come up with enough money for the church.

The Church Universal and Triumphant occupies a large swath of land just north of the park near the town of Gardiner.

Church President Kate Gordon said the 30-year grazing rights deal won't be signed until the church gets its money. State officials said that would likely be in the fall.

Lewis said Thursday that the National Park Service will contribute $1.5 million to the deal. The state will put up $300,000 and conservation groups pledged to raise the remaining $1 million.

Representatives of the Greater Yellowstone Coalition, Montana Wildlife Federation, National Wildlife Federation and National Parks Conservation Association said those groups would lead the money-raising effort.

Michael Scott with the Greater Yellowstone Coalition acknowledged the deal was only a first step toward increasing the area bison can roam outside the park. But he said the number of bison allowed through the ranch could grow over time.

Rep. Denny Rehberg, R-Mont., last year had blocked an attempt by a New York lawmaker to prod federal officials to put up money for the ranch deal. However, on Thursday, Rehberg spokesman Bridger Pierce said that opposition had not been to the deal itself but rather the way in which the money was sought.

Pierce said Rehberg considered Thursday's announcement "a small but important step" and said the government needed to find a way to eradicate brucellosis.

Lewis said the park's bison population is down by more than half from the beginning of winter to about 2,300 animals. However, she said the population remained robust and is expected to rebound in coming years.