Transcript for Former FBI director to testify before the Senate Intelligence Committee

Following the president around his trip to the middle East, several damaging stories back home. Ousted FBI director James Comey will testify before congress after memorial, think amid emerging reports that the president called Mr. Comey, quote, a nutjob. That federal probe zeroing in on the white house itself. ABC's Jon Karl also in Riyadh for us tonight. Reporter: Shortly before president trump landed in Saudi Arabia, word of a coming showdown back home. James Comey has agreed to testify after memorial, in public before the senate intelligence committee. The questions surrounding Comey's firing are mounting. I certainly would like to know the circumstances that led up to his dism and particularly those conversations, direct conversations with the president of the United States. Reporter: Trump's meeting with top Russian diplomats the day after he fired Comey is casting even more doubt on the official white house explanation for his abrupt dismissal. I just fired the head of the FBI. He was crazy. A real nutjob. Trump boasted, according to an official summary of the meeting read to "The New York Times" by because of Russia, that's taken off." Today, the Russians insisted they didn't have anything to say about Comey in that meeting. Foreign minister sergey lavrov telling reporters, "We did not touch this subject at all." But in an interview for "This week with George Stephanopoulos," national security adviser H.R. Mcmaster didn't deny president trump brought up Comey. The firing had been in the news, but I didn't know in advance that the president was going to raise it. Reporter: When repeatedly pressed, he would neither confirm nor deny the specifics of that conversation. Is that what the president said? Well, I don't remember exactly what the president said. You have the president of the United States telling the Russian foreign minister, in their first meeting, that the pressure is off because he's fired the FBI director investigating Russian interference in the campaign. Does that seem appropriate to you? As you know it's very difficult to take a few lines, to take a paragraph out of what are -- what appear to be notes of that meeting. The intent of that conversation was to say what I'd like to do is move beyond all of the Russia news so that we can find areas of cooperation. Reporter: The festering saga surely on the minds of the president's closest aides traveling with him. ABC news has learned that the FBI investigation into Russian meddling has now spread to the president's inner circle, with a senior white house aide considered a "Person of interest." Secretary of state Rex tillerson was asked who that could person be. . Jonathan Karl joins us now. The president has consistently complained about the number of leaks coming from the white house, how this compare to other administrations you've covered and are conservatives right when they warn of the so-called deep state working against the president. Reporter: Well, Tom, I don't know if I'd call it a deep state. I haven't seen anything like this. You have had multiple circumstances where details, actual transcripts of conversations the president has had in the oval office with foreign leaders have ended up on front pages of newspapers. I have never seen that with any other administration. All right, chief white house correspondent Jonathan Karl for us in Saudi Arabia. Jonathan, thank you. George will have much more from that exclusive interview with general Mcmaster tomorrow on "This week."

This transcript has been automatically generated and may not be 100% accurate.