The US moved an aircraft carrier strike group, a bomber strike force, and a number of ground forces to the Persian Gulf region, citing an undisclosed threat from Iran amid heightening political tensions between Washington and Tehran.

Kenneth Franklin "Frank" McKenzie, Commander of US Central Command, said he believes military action taken by Washington in the Persian Gulf made Iran "step back and recalculate," but the threat from Tehran remains "imminent."

Speaking to reporters in Baghdad, McKenzie said he is unsure whether US military movements made a long-lasting impression on Tehran." It is my assessment that this has caused the Iranians to back up a little bit, but I'm not sure they are strategically backing down," he told.

"They probe for weakness at all the times," he told NBC. "I would say the threat has probably evolved in certain ways even as our defensive posture has changed and become more aggressive."

"I hesitate to say that deterrence has been established," he told AP. "I don't actually believe the threat has diminished. I believe the threat is very real."

McKenzie, who took command of CENTCOM shortly before tensions with Iran began rapid escalation, was the first to request deployment of additional troops to the region, The Hill report says.

Speaking with the journalists, he noted that intelligence he has on the Iranian threat was "clear" and "compelling," adding that the alleged threats from Iran are "advanced, imminent and very specific."

McKenzie and other military officials struggle to balance between the number of forces needed to preempt an attack by showing readiness to respond defensively and deploying an excess of military forces to the region.

The US military moved an aircraft carrier strike group, a bomber task force and ground troops to the Persian Gulf region last month." Cumulatively, all of these have caused them to sort of step back and recalculate the course that they apparently were on," McKenzie said.

The nature of the alleged threat has never been publically disclosed, but some reports indicate Iran's wide-scale movement of ballistic missiles around the Gulf was a reason for concern, according to The Hill.

Joint Chiefs of Staff Chairman Gen. Joseph Dunford characterized the threat "qualitatively" different from previous ones, adding it was "more of a campaign."

Tensions between the US and Iran escalated recently when the US declared Iran's Islamic Revolution Guards Corps a foreign terrorist organization and refused to extend waivers on Iranian oil exports, cutting Tehran from a major source of revenue.

Iran denied any wrongdoing and responded by declaring US CENTCOM a terrorist organization. Tehran demanded the EU provide it with an effective mechanism to counter sanctions re-imposed by the US after unilaterally withdrawing from the so-called Iranian deal.