The following is a transcript of the interview with Democratic Representative Adam Schiff of California that aired Sunday, September 15, 2019, on "Face the Nation."

MARGARET BRENNAN: We begin this morning with the Chairman of the House Intelligence Committee, California's Adam Schiff. Good morning. Good to have you here chairman.

REPRESENTATIVE ADAM SCHIFF: Good morning.

MARGARET BRENNAN: We saw this attack that Secretary of State Pompeo says was a terror attack carried out by Iran in Saudi Arabia. What does U.S. intelligence show?

REP. SCHIFF: Well I have not had the briefing yet on whether this is directly attributable to Iran but I think it's safe to say that the Houthis don't have the capability to do a strike like this without Iranian assistance. So Iranian know-how running technology, I think was certainly involved whether the Iranians directly engaged in this or through the Houthi proxies has yet to be seen. But I think it underscores just what we really frankly came to expect from this unending war in Yemen, that it would escalate tensions in the region but also our withdraw from the JCPOA has led Iran to engage--

MARGARET BRENNAN: The nuclear deal with Iran.

REP. SCHIFF: Exactly. Has let Iran to engage in these escalatory tactics to drive us apart from our allies but also to increase Iranian leverage to try to bring about an end to sanctions.

MARGARET BRENNAN: Do you think the president should withdraw his offer to sit down and begin talks with Iran?

REP. SCHIFF: I think the president should engage in diplomacy with Iran. I think it's the only way out of this situation. I don't think, frankly, the president should have withdrawn from a nuclear deal that Iran was complying with. But we need to work with our allies to secure the Strait of Hormuz, to secure critical infrastructure in the region. But we do need to get back to diplomacy. And there are openings to do so. There are voices within Iran, unusual voices including some arch conservatives suggesting it's time to start talking with the United States again. The administration should seize that opportunity.

MARGARET BRENNAN: We also heard from the White House yesterday that they confirmed Hamza bin Laden, the son of Osama bin Laden, was killed in Afghanistan-Pakistan area. This was originally reported back in July. You've been briefed. What can you tell us?

REP. SCHIFF: Well, he- he has been killed. Good riddance. I think this is someone of great symbolic value to Al-Qaeda. Someone--

MARGARET BRENNAN: How was he killed?

REP. SCHIFF: I can't go into the specifics more than what the White House has disclosed but it shows they have acknowledged that this was in the Af-Pak region. It shows the continuing importance of that region to Al-Qaeda. It also shows the importance of the region to us in terms of our security, that we need to maintain some footprint or some guarantee that Al-Qaeda won't resurge in the area. But he was not, I think, a leader- a current leader of Al-Qaeda in an operational sense. So I think if his name wasn't Bin Laden it wouldn't have had the same impact but nonetheless an important step in terms of taking more of the leadership of Al-Qaeda off the battlefield.

MARGARET BRENNAN: Should the president continue negotiating with the Taliban?

REP. SCHIFF: The president should. I don't think the negotiations should have been called off because of a ill-planned, ill-prepared summit and it falling apart. At the end of the day there's only going to be one way to resolve the conflict in Afghanistan, that's through the negotiation. But we should secure more than Taliban promises, in that negotiation, in exchange for a drawdown of American troops. We have to insist on at least a partial cease-fire so that we can see that the Taliban are both willing but also able to control their own elements.

MARGARET BRENNAN: I want to ask you about some work you're doing here at home, which was you issued a subpoena on Friday for the acting director of intelligence alleging he's withholding a whistleblower disclosure possibly to protect President Trump. That's a pretty significant allegation here. We're putting up a quote on the screen from you. Have you gotten a response to this letter?

REP. SCHIFF: We've gotten a response and the director has said essentially that he is answering to a higher authority and refusing to turn over the whistleblower complaint. This is deeply troubling. No director--

MARGARET BRENNAN: Just ignoring the subpoena?

REP. SCHIFF: Well, at this point, yes. Ignoring the subpoena, ignoring our request. No DNI- no director of national intelligence has ever refused to turn over a whistleblower complaint. And here, Margaret, the significance is the inspector general found this complaint to be urgent, found it to be credible, that is they did some preliminary investigation, found the whistleblower to be credible, that suggests corroboration. And that it involved serious or flagrant wrongdoing. And according to the director of national intelligence, the reason he's not acting to provide it even though the statute mandates that he do so, is because he is being instructed not to. This involved a higher authority, someone above the DNI. Well there are only a few people--

MARGARET BRENNAN: Yeah.

REP. SCHIFF: --above the DNI. So we're concerned this area- this involves wrongdoing that's under investigation by our committee and we're going to do everything necessary to make sure that whistleblowers- not allowed to provide the complaint to us but can come directly to Congress, which the director is also prohibiting at this point.

MARGARET BRENNAN: So you don't know but you suspect the president has some role or the executive branch here? Can you- can you tell us what the subject was of the whistleblower complaint?

REP. SCHIFF: I can't go into the contents but I can tell you that at least according to the director of national intelligence, this involves an issue of privileged communications. Now that means it's a pretty narrow group of people that it could apply to that are both above the DNI in authority and also involve privileged communications. So, I think it's fair to assume this involves either the president or people around him or both. But at the end of the day if the director of national intelligence is going to undermine the whistleblower protections, it means that people are going to end up taking the law into their own hands and going directly to the press instead of the mechanism that Congress set to protect classified information. And that gravely threatens both our national security as well as a system that encourages people to expose wrongdoing.

MARGARET BRENNAN: You're in leadership. There seems to be confusion within the Democratic Party about whether or not there is actually an impeachment inquiry underway. Can you clarify?

REP. SCHIFF: Yes, we're doing an investigation that will ultimately determine whether the president should be impeached. Now there are people--

MARGARET BRENNAN: So there is an inquiry underway?

REP. SCHIFF: There's certainly an investigation under- underway. Now, this is about more than just message. There are some of our members who are ready to vote to impeach and remove the president tomorrow. And there are some who believe that we should not impeach him because it will be a failed exercise in the Senate. But the vast majority of our caucus, including our leadership, is of the view that we should do the investigation before we determine whether the president should be impeached. That's the category that I fit in and that's the work that we're doing. And that's all that's required in court to get access to the grand jury material we need to do our jobs.

MARGARET BRENNAN: We have to leave it there. Congressman thank you very much.

REP. SCHIFF: Thank you.