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.