President Donald Trump is being investigated by special counsel Robert Mueller for possible obstruction of justice, US media reports say.
They say senior intelligence officials will be interviewed on whether Mr Trump tried to end an inquiry into his sacked national security adviser, and about the firing of FBI chief James Comey.
Mr Trump’s legal team said the latest leak to the media was “outrageous”.
Mr Mueller is leading an FBI inquiry into Russian meddling in the election.
President Trump has repeatedly denied any collusion with Russia, describing the ongoing inquiry as a “witch hunt”.
The latest development was first carried in the Washington Post. Later the New York Times and Wall St Journal reported the story, citing their own sources.
The Washington Post said the decision by Mr Mueller to investigate President Trump’s own conduct is a major turning point in the investigation, which until recently focused on the Russian angle.