Special counsel Robert Mueller raised the notion of subpoenaing President Donald Trump in at least one meeting with the President's lawyers, two sources familiar with the matter tell CNN.

Mueller floated the possibility of subpoenaing Trump to testify before a grand jury if he refused to sit down for an interview with the special counsel, The Washington Post first reported on Tuesday, citing four people familiar with the encounter.

The exchange between special counsel investigators and Trump's lawyers, which took place in early March according to the Post, prompted Trump's then-lawyer John Dowd to respond, "This isn't some game."

"You are screwing with the work of the President of the United States," Dowd continued, two people with knowledge of his comments told The Washington Post.

One source confirmed to CNN that Dowd retorted sharply to the special counsel's suggestion. Dowd has since left the legal team.

Mueller is leading the probe investigating Russian meddling in the 2016 election and any potential connections between Trump campaign associates and the Kremlin. Trump has repeatedly denied any collusion.