The property manager of Donald Trump's Florida estate is to appear in court Monday to face charges of conspiring to help conceal the alleged mishandling of top secret government documents by the former president.

Carlos De Oliveira, 56, is scheduled to appear before a federal magistrate judge in Miami at 10:30 am (1430 GMT).

The 77-year-old Trump pleaded not guilty last month to charges of unlawfully retaining national defense information, conspiracy to obstruct justice and making false statements.

Trump, the frontrunner for the 2024 Republican presidential nomination, is scheduled to go on trial next May, at the height of what is expected to be a bitter and divisive presidential election campaign.

Special counsel Jack Smith filed additional charges against Trump in a superseding indictment last week and added De Oliveira as a defendant.

The new charges relate to Trump's alleged efforts to obstruct the FBI investigation and its bid to recover classified documents the former president took with him when he left the White House.

Trump is specifically accused in the latest indictment of attempting to "delete security camera footage" at Mar-A-Lago to prevent it from being provided to the FBI and a federal grand jury.

Also charged are Trump's personal aide Waltine "Walt" Nauta and De Oliveira.

Nauta, a 40-year-old US Navy veteran from Guam, served as Trump's military valet while he was president and has continued working for him in a personal capacity since he left the White House.

Trump, Nauta and De Oliveira allegedly sought to have another Trump employee, who is not identified in the indictment, delete security camera footage at Mar-A-Lago.

De Oliveira, according to the indictment, allegedly told "Trump Employee 4" that "the boss" wanted the server containing security camera footage of a storage room deleted.

De Oliveira is additionally charged with making false statements to the FBI.

Asked if he ever helped unload or move boxes of documents at Mar-A-Lago, De Oliveira said he had not.

"Never saw nothing," he said.

The twice-impeached former president is accused of endangering national security by holding on to top-secret nuclear and defense information after leaving the White House.

Trump kept the files unsecured at Mar-a-Lago -- a club that entertains thousands of members and guests every year -- and thwarted official efforts to retrieve them, according to the indictment.

Trump faces other legal woes including a looming indictment from Smith for the former president's attempts to overturn the 2020 presidential election won by Democrat Joe Biden.

Trump also faces multiple felony counts in a New York fraud case involving alleged hush money payments to porn star Stormy Daniels.