Law enforcement officials have said they would not provide details of their plans to resolve the standoff. The militants said they would continue occupying the government building for "as long as it takes."
US Federal Bureau of Investigation (FBI) officials on Monday said they were seeking a "peaceful" end to a weekend occupation of a federal building in Oregon by armed self-styled militiamen, who said they were protesting the arrest of fellow ranchers.
"The FBI is working with the Harney County Sheriff's Office, Oregon State Police and other local and state law enforcement agencies to bring a peaceful resolution to the situation at the Malheur National Wildlife Refuge," said the FBI's Oregon office in a statement.
Armed protesters on Saturday occupied a federal building of the national wildlife refuge in Oregon. They were led by Ammon Bundy, the son of Cliven Bundy, a Nevada rancher who also staged an armed protest against federal land management officials in 2014.
"Due to safety considerations for both those inside the refuge as well as the law enforcement officers involved, we will not be releasing any specifics with regards to the law enforcement response," the bureau added.
The anti-government militants said they occupied the building to show solidarity with ranchers Dwight Hammond, 73, and his son Steve, 46, who both face imprisonment for starting fires that engulfed more than 139 acres of federal land. The militants vowed to continue occupying the building for "as long as it takes."
However, the Hammonds replied swiftly to the ongoing situation in a bid to distance themselves from the occupying group.
"Neither Ammon Bundy nor anyone within his group/organization speak for the Hammond family," said a statement from W. Alan Schroeder, a lawyer representing the family, according to local media.
The US Fish and Wildlife Service (FWS) announced late Sunday night that all staff at the federal refuge "are safe and accounted for."
ls/msh (Reuters, AFP, AP)