A U.S. official tells Fox News that Iran has been at a state of readiness to launch an attack on Israel within 12 to 24 hours since early August following the July 31 assassination of Hamas leader Ismail Haniyeh in Tehran.

In recent days the U.S. has seen additional movement of missiles in Iran to prepare for the now “imminent” attack, the official said. Iran could launch its attack as soon as this afternoon, U.S. officials also said.