THIS JUST IN:

FBI and DEA agents have disrupted a plot to commit a "significant terrorist act in the United States" tied to Iran, federal officials told ABC News today.
The officials said the plot included the assassination of the Saudi Arabian ambassador to the United States, Adel Al-Jubeir, with a bomb and subsequent bomb attacks on the Saudi and Israeli embassies in Washington, D.C.

Bombings of the Saudi and Israeli embassies in Buenos Aires, Argentina, were also discussed, according to the U.S. officials.

The stunning allegations come against a backdrop of longstanding tensions between Iran and the United States and Saudi Arabia. In the last year, Saudi Arabia has attempted to build an anti-Iran alliance to push back against perceived aggression by Iran in the region.