If the Iranians needed a motive to assassinate Saudi Arabia’s ambassador to the United States they may have found it in a diplomatic cable leaked earlier this year by WikiLeaks.

In the April 20, 2008 cable, Ambassador Adel al-Jubeir relayed to America’s No. 3 diplomat in Riyadh that the Saudi king wanted the U.S. to attack Iran’s nuclear program. “He told you to cut off the head of the snake,” the cable quotes al-Jubeir as saying.

The Justice Department on Tuesday released a criminal complaint accusing an Iranian-American man of acting on behalf of Iran’s elite Quds Force to pay the Mexican drug gang Los Zetas to kill al-Jubeir. Iran has vehemently denied any involvement.

House Intelligence Committee Chairman Mike Rogers (R-MI) told The Daily Beast on Thursday that the plot against the Saudi diplomat brought to light the threat Iran’s Quds force posed to America and its allies. He also said the leaked cable was one of many reasons that the Iranians sought to kill the Saudi ambassador.

“I am sure it was one of many things,” Rogers told The Daily Beast. “He (al-Jubeir) was seen as one of the most vocal critics of Iran too.” Rogers added that Iran and Saudi Arabia have had tensions between them for a long time, but that Iran “thought the environment was ripe to put this together.”

A federal law enforcement official told The Daily Beast that the government is still trying to determine what “prompted Quds Force to undertake this alleged plot,” and that officials can’t say for sure whether the cable itself was a factor.

Nonetheless, the administration has been escalating its pressure on Iran since the indictment. President Obama declared Thursday that the evidence that Iran was involved in the plot was strong, and he intends to seek sanctions against Tehran. State Department spokeswoman Victoria Nuland also said Thursday that U.S. diplomats had made direct contact with Iranian diplomats to express Washington’s displeasure. U.S. officials tell The Daily Beast that the communication was made in New York to Iran’s United Nations mission.

Rogers said the criminal complaint Tuesday “was the first public light of what the Quds Force has been up to for years.” He added, “Other than al Qaeda, they have more American blood on their hands than any other terrorist group. They are very good, and they have nation-state backing, they have all the institutions and support, they have time to train, and they have the ability to move.”

The case in many ways was the result of two agencies that often are not credited in the counterterrorism world: the Drug Enforcement Agency (DEA) and the Department of Treasury. The DEA first learned of the scheme from an informant who was approached by Manssor Arbabsiar, the Iranian-American charged Tuesday in the murder-for-hire plot. The DEA then worked with Arbabsiar to set up more meetings, leading eventually in August to Arbabsiar arranging for nearly $100,000 to be wired into an account belonging to an undercover agent.

U.S. officials tell The Daily Beast that they knew the Quds Force was behind the plot when the money was transferred in part because the Treasury had monitored the overseas account and identified it long before as an account used by the Iranian organization for supporting operations overseas. “We believe the information is ironclad,” one U.S. intelligence official told The Daily Beast. This official added that other technical intelligence confirmed that this was a Quds Force plot, and that Arbabsiar was not working on his own.

On Thursday Rogers acknowledged that some observers looked at Arbabsiar, who had a reputation for smoking marijuana and was considered to be unreliable by many who knew him, and concluded the plot may be “amateurish.”

“Call it amateurish, [but] if you look at the way they tried to do the cut-outs on this, it was sophisticated,” he said. Cut-outs refer to third parties in the intelligence trade that obscure the responsibility of the nation’s service in an operation. Rogers said the plot may have succeeded if Arbabsiar had not made the mistake of reaching out to an informant. “One of the best intelligence services in the world is the Russians, and the Iranians are not too far behind,” Rogers said.

In some ways, the threat from the Quds Force and Iran is not entirely new.

Juan Zarate, who served as a deputy national security adviser dealing with counterterrorism under President George W. Bush, said, “We have been concerned about the Iranian reach into North and South America for some time now. In a certain way this is comforting, this is a very sloppy, poorly executed attack plan. On the other hand, I don’t think this should lull us into a sense of security of what Iran is capable of.”

Michael Leiter, who stepped down this year from his post as director of the national counterterrorism center, told the Senate last September that he believed Hizbullah, a group with strong backing from the Iranian government, had the capability to launch an attack in the United States.

When asked “Do you think if there’s an escalation between Iran and Israel that we will see more of a threat here in the United States?” Leiter responded with one word, “yes.”

Hizbullah does not engage in military operations overseas unless there are representatives and advisers from Iran’s Revolutionary Guard, which would coordinate the operation, said Ali Alfoneh, an expert on Iran’s revolutionary guard corps at the American Enterprise Institute. The Quds Force is an elite external operational arm of the revolutionary guard corps.

Suspicions that Iran might try to strike on U.S. soil have been around for years. Between 2002 and 2006, the Bush administration expelled at least six Iranian diplomats from the United Nations for spying, on the ground that the diplomats were casing subway lines in New York City.

Sen. Chuck Schumer (D-NY) said in 2004, “I can’t think of a single good reason why anyone would be videotaping how the subway works in the middle of the night—not one. If we are ever going to trust Iran’s cooperation in the War on Terrorism, we need to get some answers to these questions right now.”