Special Counsel Robert Mueller, in a meeting with President Donald Trump's lawyers in March, raised the possibility of issuing a subpoena for Trump if he declines to talk to investigators in the Russia probe, the Washington Post reported on Tuesday.

Citing four people familiar with the encounter, the Post said Mueller mentioned a subpoena after Trump's lawyers said the president had no obligation to talk with federal investigators who are probing Russia's alleged meddling in the 2016 presidential election.