James Comey, the former FBI director, and Jeff Sessions, the US attorney general, have both been interviewed by the Russian election meddling investigation, it emerged on Tuesday.
Mr Comey answered questions from the team of Robert Mueller, the special counsel, before Christmas while Mr Sessions was interviewed last week.
The pair are both central to one of Mr Trump‘s most controversial decisions in office – the firing of Mr Comey, who at the time headed up the Russia investigation.
Critics have questioned whether the move amounted to obstruction of justice – one of the grounds for impeachment of a president.
Mr Sessions is the first member of Mr Trump’s cabinet to be interviewed by the Mueller investigation.
The former Alabama senator was one of Mr Trump’s most vocal supporters in his presidential campaign and played a central role advising on foreign policy.
Since taking office their relationship has soured after he stepped away from any involvement in the Russia investigation, despite the president opposing the move.
Mr Comey, fired last May, was reportedly asked about a series of memos about Mr Trump’s behaviour he wrote before his departure.
One said that Mr Trump asked him to end the FBI investigation into Michael Flynn, the former national security adviser. This has been disputed by the president.
Mr Sessions is the latest key figure of the Trump team to be interviewed by Mr Mueller, who appears to be nearing the end of his investigation.
Steve Bannon, Mr Trump’s former campaign manager, has agreed to be questioned, while Hope Hicks, the White House communications director, and Mr Trump himself reportedly are wanted for interview.
The investigation is looking at all Russian election meddling – including the alleged hacking of Democratic Party emails and social media advertising as well as how the Trump campaign behaved.
In a separate development, it was reported that Christopher Wray, the current FBI director, threatened to resign over demands for personell changes from Mr Sessions and Mr Trump.
Axios, the political news website, reported that Mr Wray opposed calls to remove Andrew McCabe, the deputy FBI director, from Mr Sessions. Mr Trump had publicly suggested the move.
Three sources with “direct knowledge” said Mr Wray had threatened to quit if Mr McCabe was removed, according to Axios.
Mr Comey, the former FBI director, appeared to respond to the news in a tweet: “Good to read reports of people standing up for what they believe in. ‘The ultimate measure of a man is not where he stands in moments of comfort and convenience, but where he stands at times of challenge and controversy’ — MLK.”