Police in major US cities are on alert for potential unrest in case former President Donald Trump is arrested this week as part of a hush-money inquiry.
Authorities in New York, Washington DC and Los Angeles are ramping up their law enforcement presence.
A Manhattan prosecutor is considering whether to charge Mr Trump over hush-money payments to a porn star.
It would be the first criminal case ever brought against a former US president.
Steel barricades were being erected outside the Manhattan Criminal Court on Monday, where Mr Trump could be charged, fingerprinted and photographed if charges are filed this week, as US media widely anticipate. Increased police presence has also been seen outside Trump Tower in the city.
Every member of the New York Police Department (NYPD), including plainclothes detectives, has been ordered to wear their full uniform on Tuesday and is being placed on standby to mobilise, a police source told CBS, the BBC’s US partner.
The NYPD and the FBI’s Joint Terrorism Task Force have been in touch with the US Secret Service, whose job it is to protect presidents and former presidents, about how a potential arrest might take place.
Capitol Police, who protect lawmakers on Capitol Hill in Washington DC, plan to issue an emergency declaration on Tuesday, a congressional source told CBS.
The order aims to increase co-ordination with other law enforcement agencies.
More civil disturbance officers will also be on standby, though the congressional source said there was no specific threat and that the order was proactive.
In Los Angeles, the LAPD and federal officials were preparing for a pro-Trump protest on Tuesday outside a federal building, the LA Times newspaper reports.
US intelligence officials have detected an uptick in online threats against legal and government officials since Mr Trump wrote online on Saturday that he was expected to be arrested on Tuesday, according to CBS.
Most of the threats were against Manhattan District Attorney Alvin Bragg, the man widely expected to file charges against Mr Trump.
On Saturday, the same day Mr Trump posted that his supporters should protest, Mr Bragg sent an email to staff.
“We do not tolerate attempts to intimidate our office or threaten the rule of law in New York,” Mr Bragg wrote.