Security levels will be strengthened starting Tuesday morning, the sources told the news outlet, adding that bicycle rack-type fencing could be deployed as well.
Some police intelligence officers have also suggested that mass protests may take place near Trump's residence at a Mar-a-Lago resort and in New York City, rather than in front of the US Capitol.
On Saturday, Trump said on his social media platform, Truth Social, that he expected to be arrested on March 21 and called on his supporters to protest. Trump criticized a "corrupt and highly political" Manhattan District Attorney's Office for trying to arrest him based on "old and fully debunked" charges.
Trump's possible arrest is reportedly connected with alleged illegal payments to adult film star Stormy Daniels in 2016 in a bid to prevent her from disclosing her 2006 sexual affair with him. Trump has denied all accusations.