"There has been consistent intelligence in the last several weeks," one administration official told CNN.
A second official described it as information that has been gathered throughout November. The information is being gathered by military and intelligence agencies.
The officials would not say in what format the intelligence exists. But in the last several weeks there has been movement of Iranian forces and weapons that the US worries could be put in place for a potential attack, if one is ordered by the Iranian regime, the officials said. It's not clear if a potential threat would come from the central government or Iran's Islamic Revolutionary Guard Corps.
The head of US military operations in the Middle East recently signaled the US expects some kind of Iranian action in response to the US sanctions and pressure campaign that is trying to get the regime to abandon its nuclear program.
"I would expect that if we look at the past three or four months, it's possible they will do something that is irresponsible. It's possible that they'll lash out at their neighbors," Gen. Kenneth McKenzie, head of the US Central Command, told an audience in Bahrain at the time. "It is not going to be productive for them in the long term to choose to act out in the military domain. That's the message that we're trying to convey."
The Pentagon did allow the carrier USS Abraham Lincoln to enter the Persian Gulf and conduct a port visit in Bahrain during the Thanksgiving holiday. But officials said specific precautions were taken, given the threat, although they would not say what those precautions were.
The carrier is now expected to stay in the region until the next carrier, the USS Harry S. Truman, moves closer, from its current position in the eastern Atlantic Ocean.
Officials were adamant the intelligence has been gathered solely as part of the continuous monitoring by the US and has nothing to do with President Donald Trump's political concerns over the impeachment inquiry. The intelligence has moved through professional military and intelligence channels, and it is not clear whether Trump has yet been briefed on it in detail.
There is also not a full US understanding of to what extent the current unrest in Iran may be playing a role in the regime's decision making.
The US has said the Iranians conducted several provocations against commercial shipping in the Persian Gulf earlier this year and was also responsible for a massive drone attack on Saudi Arabia's oil infrastructure. That led to the deployment of fighter jets and anti-missile systems to Saudi Arabia. The two countries are still discussing the exact monetary amount Saudi Arabia will reimburse the US for that deployment of protective forces.
While not commenting on the current intelligence, Cmdr. Rebecca Rebarich, a Pentagon spokeswoman, told CNN, "We continue to closely monitor the activities of the regime in Iran, its military and its proxies, and we are well postured to defend US forces and interests as needed."
Several weeks ago, Defense Secretary Mark Esper told reporters the administration was pleased to see a "downtick" in overt Iranian actions in the region and that the administration wanted to send a signal "that the path forward is through diplomacy," but the military is "prepared to act as need be."