Special Counsel Robert Mueller warned he could order Donald Trump to testify as part of a probe into alleged Russian election meddling, US media report.
Mr Mueller suggested the move during talks with Mr Trump's lawyers in March.
The threat to issue a subpoena, as it is known, was reportedly met with a sharp response from one of Mr Trump's former lawyers.
It is believed to be the first time the special counsel has raised such a possibility.
Mr Trump's lawyers insisted during the meeting that the president was under no obligation to face questions by federal investigators in relation to the Russia inquiry, the Washington Post reported.
However Mr Mueller's team reportedly responded by suggesting they would issue a subpoena if Mr Trump declined. They agreed to provide the president's lawyers with more specific information about the questions they wished to ask Mr Trump.
The president's former lawyer, John Dowd, has also said that Mr Mueller mentioned the possibility of forcing Mr Trump to face questions.
Mr Dowd, who resigned about a week and a half after the meeting, said he told investigators that the probe was not "some game", adding: "You are screwing with the work of the president of the United States."
The list of possible questions has since been published in the New York Times, and it reportedly covers the president's motivations in dismissing former FBI director James Comey last May and his campaign's contacts with Russia.
Mr Trump has called the leak "disgraceful", repeating his claim that the Russia inquiry is a "witch hunt".
