The United States is prepared to defend "Israel" in the event of an Iranian attack, White House national security spokesperson John Kirby said on Tuesday, referring to Iran's vowed retaliatory operation in response to the Israeli assassination of Hamas' chief politburo martyr Ismail Haniyeh in Tehran last month.

Talking to Israeli Channel 12, Kirby said that Washington takes Iran's rhetoric seriously, but it is difficult to estimate the chances of a retaliation taking place.

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"We believe that [Iran is] still postured and poised to launch an attack should they want to do that, which is why we have that enhanced force posture in the region," he told the news outlet.

Following the Israeli assassination of Haniyeh during his official visit to Tehran, Washington neither condemned the attack nor criticized the violation of the Islamic Republic's sovereignty and security.

"Our messaging to Iran is consistent, has been, and will stay consistent. One, don't do it. There's no reason to escalate this," Kirby said without mentioning the Israeli aggression.

"There's no reason to potentially start some sort of all out regional war. And number two, we are going to be prepared to defend Israel if it comes to that," he continued.

In recent weeks, the US military has increased its presence in the Middle East in an attempt to deter large new strikes by Iran or its allies, sending the Abraham Lincoln aircraft carrier strike group to replace the Theodore Roosevelt carrier strike group.

Hezbollah carried out on Sunday its "initial response" to the Israeli assassination of its senior military commander Sayyed Fouad Shokor last month in Beirut. The Israeli airstrikes on a residential building also resulted in the martyrdom of five civilians: three women and two children, in addition to tens of wounded.

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Commenting on Hezbollah's response, the chairman of the US Joint Chiefs of Staff told Reuters on Monday that the Resistance's retaliatory operation was "one of two major threatened attacks against Israel."

While the operation did not lead to any direct threats of escalation, General Charles Q. Brown Brown said "it depends on how the second is going to play out," referring to the Iranian response.

Although the top general confirmed that the risk of a regional war has "somewhat" decreased, he still cautioned that the impending Iranian operation would determine the fate of the region. 

"How Iran responds will dictate how Israel responds, which will dictate whether there is going to be a broader conflict or not."

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