Mueller told Trump's lawyers he could 'compel' president to testify via subpoena

Special Counsel Robert Mueller told Donald Trump's legal team directly he could "compel" the president to testify via a grand jury subpoena if Trump declined a potential request for an interview, two sources told ABC News.

For the last several months, the Trump legal team has been in active negotiations with Mueller's team pursuing such an interview, which would include either a face-to-face interview with parameters, a written questionnaire or some mix of the two, according to two sources familiar with the conversation from a meeting in early March.

The possibility of a presidential subpoena by Mueller was first reported by the Washington Post.

Trump's former lead attorney John Dowd told ABC News that Mueller raised the possibility of a subpoena in that meeting.

"This isn't some game. You are screwing with the work on the president of the United States," Dowd said he told investigators in response.

Negotiations stalled in March because of Dowd's abrupt departure, but talks resumed in recent weeks after Rudy Giuliani joined the legal team.

Trump's lawyers created a list of 49 questions based off the ongoing negotiations with Mueller's team and centered around areas the special counsel would like to ask the president.

Sources familiar with the list confirmed its authenticity to ABC News after the New York Times published the list of questions.

Trump’s lawyers and the special counsel's office each declined to comment to ABC News.