This week on Brian Ross investigates. Iran crosses the line. A stunning terror -- the US says it was directed from Tehran with a bomb set to go off across Washington DC. Targeting the Saudi... See More
This week on Brian Ross investigates. Iran crosses the line. A stunning terror -- the US says it was directed from Tehran with a bomb set to go off across Washington DC. Targeting the Saudi ambassador. To Saudi and Israeli embassy and was this an act of war. What do the US do not. -- and Richard Clarke has the -- Brian Ross investigates. Welcome I'm Brian Ross in New York it's a stunning allegation. As described by the US factions in the Iranian government directed and paid for a convoluted plot to murder Saudi ambassador to Washington. And carry out follow up bomb attacks on Saudi and Israeli embassies in the capital. If that have been carried out as the US says Iran what dozens of people would have been killed and it could well have been considered an act of war. US officials say the Iranians one of the -- set off at a Capitol Hill restaurant. And did not care -- dozens of innocent Americans die. When the confidential source noted that there could be 100 -- 150 people in a fictional restaurant. Where the requested bombing would take place the lead defendant said no problem. And no big deal. The prime target was the youthful Saudi Arabian ambassador to the United States -- knowledge of -- We are resolved to fight terrorism a close confident that the Saudi king and a prominent symbol of a government that has increasingly been the arch enemy of Iran in the region. This conspiracy was conceived. Sponsored. And was directed from Iran in a criminal complaint that was compared to a Hollywood script officials said an Armenian American from Corpus Christi, Texas. 56 year old months -- -- Bob CR was recorded offering a million and a half dollars from Iran for the ambassador of murder. In one phone call to -- recorded by the FBI are -- are reportedly referred to the terror plot with the code word Chevrolet. -- -- -- I wanted to tell you the Chevrolet is ready it's ready to be done I should continue right yes yes yes. Our Bob ZR is now in custody but FBI agents were at his home and Austin, Texas Tuesday where his wife later defended. It was it the wrong place at the wrong time I'm sure of that. -- I know that you finished since is gonna come out. Officials say are Bosnia thought He was dealing with a member of a Mexican drug cartel. Who was in fact a government informant if the -- had not been for we would be looking at a military confrontation this is a provocation. And there's no other way of looking at it. The most damning evidence -- some 100000. Dollars that the US says came from the arrangements wired to an FBI undercover bank account. A down payment for to -- Secretary of state Hillary Clinton says. And vice president Joseph Biden says all options for response to remain on -- it. To talk about that we are joined by former White House counterterrorism advisor Richard Clarke on ABC news consult. The director the FBI said this compares to a Hollywood script. That might be that Hollywood might turn down -- so -- Seemingly not realistic. Do you buy that -- what we've been told about what. Well we know this we know that there there's a lot of tension between Saudi Arabia and Iraq. We know that the -- special forces that could force. Operate using cutouts using circuits. Now they've never used a Mexican drug gang before that I'm aware of but it's not inconceivable that if you wanted to do something in the United States. He would need a new cut out a new surrogate and you look around and who would you -- Few would find a gang very well organized gang in the Zito gang in Mexico. That has no hesitation about killing people assassinating people does it very well with regularity. Does a lot of things for money. It's not inconceivable that you tried to reach out to lose it again. Now whether you use this particular route to do that. Seems a little unclear to me. But the overall plot is not so crazy. President Obama made much when He came into office about -- -- and doesn't seem to -- what would your advice be for him now about what to do about. This what to do about Iraq. Well at least to reach out four and the Iranian government response. And through a number of different channels much -- the diplomatic channel but also through intelligence contacts and military contact. And say to them. What was this. Because unless you can prove to us otherwise we're going to assume. That this was the major provocation that you had decided as a government. To cross this red line. Across the room -- -- and staged terrorist attacks in the capital of the United States. I think we need to probe and see what their responses. And see if one faction that we're the other. -- Iran says well wait a minute we didn't know about this it was the other guys. Beyond that what can we do we can ratchet up sanctions. But frankly Brian we're running out of sanctions. Mr. Clark thank you very much for continuing coverage on the story and other investigative reports but abcnews.com. And click on investigative. You can also follow me and the ABC news investigative team FaceBook and Twitter. Thanks for joining. We'll have more on this story as is the -- I'm Brian Ross in the.
This transcript has been automatically generated and may not be 100% accurate.