Vice President Joe Biden said today that "nothing has been taken off the table" when it comes to the U.S. response to an alleged plot by Iran to assassinate the Saudi Arabian ambassador to the U.S. and unleash deadly terrorist bombings in Washington, D.C.

"It is an outrageous act that the Iranians are going to have to be held accountable," Biden told ABC News' "Good Morning America". "This is really over the top."

U.S. Attorney General Eric Holder announced Tuesday the DEA and FBI had disrupted a plot "conceived, sponsored and... directed from Iran" to murder the Saudi Arabian ambassador to the U.S. in or outside a crowded Washington, D.C. restaurant which potentially would have been followed up by bombings of the Saudi Arabian and Israeli embassies. The U.S. said an Iranian-American, 56-year-old Manssor Arbabsiar of Corpus Christi, Texas, was working for elements of the Iranian government when he attempted to hire hitmen from the feared Zetas Mexican drug cartel to carry out the hit, but Arbabsiar was unwittingly speaking to a DEA informant from the start.

READ: U.S. Complaint in Alleged Iran-Directed Terror Plot (PDF)

Senior Obama administration officials had previous told ABC News the U.S. response would not include the possibility of an armed conflict with Iran and -- though a complaint filed in federal court directly tied Iran's elite Quds military unit to the plot -- there was no information that Iran's top leaders were aware or had any role.

Biden said the U.S. was in the process of "uniting world opinion" against Iran as it goes forward with a response. The U.S. Treasury Department announced Tuesday sanctions against five Iranians allegedly tied to the plot.

READ: U.S. Will Not Respond Militarily to Iran Over Assassination Plot

A lawyer for Arbabsiar has not returned requests for comment, but the man's wife, Martha Guerrero, said he was wrongly accused.

"I may not be living with him being separated, but I cannot for the life of me think that he would be capable of doing that," she told ABC News' Austin affiliate KVUE, noting the two had been separated some time. "He was at the wrong place at the wrong time. I'm sure of that."

Iranian officials have strongly rejected the U.S. accusations, calling them a "fabrication." The head of the Iranian mission to the United Nations penned a letter Tuesday to U.N. Secretary General Ban Ki-moon expressing "outrage" at the allegations.

"The U.S. allegation is, obviously, a politically-motivated move and a showcase of its long-standing animosity towards the Iranian nation," the letter says. "The Islamic Republic of Iran categorically and in the strongest terms condemns this shameful allegation by the United States authorities and deplores it as a well-thought evil plot in line with their anti-Iranian policy to divert attention from the current economic and social problems at home and the popular revolutions and protests against United States long supported dictatorial regimes abroad."

Alleged Terror Plotter Claims He Was 'Directed By High-Ranking' Iranian Officials

The new case, called Operation Red Coalition, began in May when Arbabsiar unwittingly approached a DEA informant seeking the help of a Mexican drug cartel to assassinate the Saudi ambassador, according to counter-terrorism officials.

Arbabsiar reportedly claimed he was being "directed by high-ranking members of the Iranian government," including a cousin who was "a member of the Iranian army but did not wear a uniform," according to a person briefed on the details of the case.

Arbabsiar and a second man, Gohlam Shakuri, an Iranian official, were named in a five-count criminal complaint filed Tuesday afternoon in federal court in New York. They were charged with conspiracy to kill a foreign official and conspiracy to use a weapon of mass destruction, a bomb, among other counts. Shakuri is still at large in Iran, Holder said.

Holder identified Shakuri as an Iran-based member of the Quds force.

Arbabsiar, a naturalized U.S. citizen, expressed "utter disregard for collateral damage" in the planned bomb attacks in Washington, according to officials.

The complaint describes a conversation in which Arbabsiar was allegedly directing the informant to kill the Saudi ambassador and said the assassination could take place at a restaurant. When the informant feigned concern about Americans who also eat at the restaurant, Arbabsiar said he preferred if bystanders weren't killed but, "Sometimes, you know, you have no choice, is that right?"

U.S. officials said Arbabsiar met twice in July with the DEA informant in the northern Mexico city of Reynosa, across the border from McAllen, Texas, and negotiated a $1.5 million payment for the assassination of the Saudi ambassador. As a down payment, officials said Arbabsiar wired two payments of $49,960 on Aug. 1 and Aug. 9 to an FBI undercover bank account after he had returned to Iran.

Officials said Arbabsiar flew from Iran through Frankfurt, Germany, to Mexico City Sept. 29 for a final planning session, but was refused entry to Mexico and later put on a plane to New York, where he was arrested.

Officials said Arbabsiar is now cooperating with prosecutors and federal agents in New York, where the case has been transferred.

"Though it reads like the pages of a Hollywood script, the impact would've been very real and many lives would've been lost," FBI Director Robert Mueller said of the foiled plot.

ABC News' Richard Esposito and Jake Tapper contributed to this report.