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 about whether Mr Trump tried to end an inquiry into his sacked national security adviser.
Mr Trump’s legal team said the latest leak to the media was “outrageous”.
Mr Mueller is overseeing an FBI inquiry into Russia’s alleged meddling the 2016 US election and any Trump links to it.
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.