In a 29-page report released Friday, FBI agents argue that the spending cuts and possible furloughs are a threat to public safety, The Washington Post reported.
"We feel incredibly frustrated and find it very disturbing that we are going to be restrained from protecting Americans from criminal and terrorist attacks," said Rey Tariche, an FBI special agent and president of the FBI Agents Association, which wrote the report, titled "Voices From the Field."
FBI Director James Comey, who took office this month, said he was stunned by the impact the sequester has had on the FBI.
"I'm not crying wolf," Comey said. "I'm not playing a game. This is the FBI. We will salute and execute. But I was very surprised to learn how severe the required cut is -- and the potential impact on the FBI."
The FBI is in a hiring freeze and may be required to cut its budget by 10 percent, or $800 million, which Comey said would force him to eliminate 3,000 positions.
Comey said he may have to furlough the FBI's 36,000 employees for two weeks without pay.
Comey said the FBI Academy in Quantico, Va., "is quiet."
"I have no new agent classes going through there," he said. "I can't afford it."