BILLINGS, Mont. (AP) -- Bison could roam year-round in large areas adjacent to Yellowstone National Park under a proposal from Montana officials who want to further ease longstanding restrictions on the animals.

The plan announced Monday would allow bison to remain year-round in the Hebgen Basin and surrounding areas west of the park and in the Gardiner Basin to the north.

The Gardiner area would be restricted to bull bison only except during winter.

For decades migrating bison have been slaughtered or hazed back into the park to prevent them from passing the disease brucellosis to cattle.

Current rules allow some bison to migrate to grazing areas in Montana each winter. They must return to the park each spring.

Conservationists want more room for bison, while ranchers say they remain a disease threat.

Copyright 2012 The AP.