WASHINGTON (Reuters) - U.S. spy and law enforcement agencies on Friday said they had strengthened procedures for informing Congress, state and local governments, private business and the public about foreign interference in U.S. elections.

People vote at electronic polling stations in Huntington Beach, California, U.S. November 6, 2018. REUTERS/Mike Blake - RC1170E35000

The FBI has already given some American election candidates “defensive” briefings on evidence U.S. agencies collected of possible election interference, an FBI official told a briefing for journalists.

The official, who spoke on condition of anonymity, declined to give further details regarding who might have been warned about the interference or where and how such interference might have originated.

An official, also speaking on condition of anonymity, said that U.S. agencies believe that Russia, China and Iran all present continuing potential threats to the U.S. electoral system. However, officials stressed that U.S. agencies had not seen direct threats to American election systems recently.

An FBI official added that the bureau has “invested a lot of time” in trying to help social media companies detect inauthentic politically related message traffic, and shares information on this with social media companies.

Officials said that President Donald Trump on Oct. 31 had approved spy and security agency plans to step up election security, but said they were unaware whether he had issued a written order confirming this.

Officials said enhanced notification procedures are being activated by the FBI, the Department of Homeland Security and the Cyber and Infrastructure Security Agency to supplement procedures already used by federal agencies to notify victims of crime, including computer hacking or other crimes directed against political campaigns.

The officials said that parties who could receive such notifications include targets of election interference, Congress and the public.

In a briefing paper on the new notification procedures, agencies involved said that the need to protect sensitive national security sources and methods would be considered when officials are deciding whether or not to issue an interference notification.

The paper said the Secret Service would be informed of any evidence of foreign political interference directed against major U.S. presidential and vice presidential candidates in the November 2020 election as well as organizations and events in which they participate.

One official said victims and targets of election-related interference “would not have a veto” over who federal authorities would notify about such interference, though security and political sensitivities would certainly be considered before such notifications are undertaken.