The brazenness of the plot outlined by Justice Department officials struck many current and former U.S. officials as out of character for Iran, which has rarely, if ever, been so bold as to strike targets in America. U.S. officials were similarly surprised last month when an Iranian admiral threatened to send naval ships to patrol off U.S. waters.

“To my mind, it reeks of desperation,” said Matthew Levitt, a former deputy assistant treasury secretary for intelligence and analysis. “It suggests to me that they are feeling cornered.”

To others, the very rashness of the alleged assassination plot raised doubts about whether Iran’s normally cautious ruling clerics supported or even know about it. Robert Baer, a former CIA case officer in the Middle East and author of several books on Iran, said there was “sloppiness about the case that defies belief.”

“Maybe things have really fallen apart in Tehran, or maybe there’s a radical group that wants to stir up the pot,” Baer said. “But the Quds are better than this. If they wanted to come after you, you’d be dead already.”

Other current and former U.S. officials argued that the plot had to have originated at the highest levels of Iran’s government and the elite Revolutionary Guard Corps, given the costs and complexities of conducting such an international operation.

“A reasonable person can conclude that senior members of the [Revolutionary Guard] and Quds Force and the civilian government had to know,” said Mike Rogers (R-Mich.), chairman of the House intelligence committee.

The plot shows that the Iranians “have gotten more and more brazen,” he said. “This was a two-fer for them: kill the Saudi ambassador and embarrass the United States by having it happen on U.S. soil in Washington, D.C.”

Administration officials made clear that they saw the plot as a high-level operation, not the work of rogue agents.

“The United States does not need new reasons to have serious concerns about the Quds Force,” said a senior administration official, citing the militant force’s role in Iraq, Lebanon and other strategic places. “But this plot on U.S. soil is a dangerous escalation, and we consider it a flagrant violation of international law.”