National Archives advises White House to preserve all Trump tweets, including deleted ones

The agency points to the Presidential Records Act of 1978.

Ferriero also wrote that White House officials have informed the National Archives that they "are, in fact, doing so," but did not detail the process for doing so.

The National Archives briefed the White House counsel's office on the records act in February, and has since been in communication with the office on a "regular basis," the letter states.

The Presidential Records Act "places the responsibility for the custody and management" of records with the president. The National Archives can only advise the Office of the Counsel in collecting presidential records.

If President Trump wants to dispose of any of his records that "no longer have administrative, historical, informational or evidentiary value," he would have to first consult with Ferriero and obtain his written views.

President Trump has two Twitter accounts -- @realDonaldTrump and @POTUS – from which he posts regularly. McCaskill, Carper and other critics are concerned that Trump may be violating the Presidential Records Act when he deletes tweets.

One such example came on Inauguration Day when Trump tweeted and deleted, "I am honered to serve you, the great American People, as your 45th President of the United States!"

He then posted another tweet immediately after with the same wording, but correctly spelling "honored."

House Oversight Committee leaders also sent a letter March 9 to the White House counsel's office, asking for more details on how it's conducting the records preservation.

The White House did not immediately respond to ABC News' request for comment.