While domestic attention this week is focused on the Ukraine impeachment saga, our foreign policy attention is on China and North Korea. But we would do well to keep a close eye on Iran as well.

As U.S.-Iran tensions escalate and Iranian attacks, such as the recent strikes against Saudi oil facilities, go largely unpunished, there is a growing risk that Iranian hardliners will attack U.S. interests. My specific concern is that Iran will go beyond shooting down American drones, and instead endanger American lives. There are two issues here.

First off, Supreme Leader Ayatollah Ali Khamenei's unwillingness to give President Hassan Rouhani the political space to renegotiate the 2015 nuclear accord. That obstruction means President Trump lacks reason to release Iran from the crippling sanctions it currently endures. Khamenei also blames Rouhani for failing to persuade the European Union to provide a remedy to U.S. sanctions. This has weakened Rouhani's influence with Khamenei (relegating the president to inane speeches), while strengthening the hardliners' position.

That brings us to the problem of the hardliners' nature. Vested with a fanatical hatred of America, the Islamic Revolutionary Guard Corps hardliners are willing to roll the dice when they can contain the fallout of doing so. The key here is that they do not view American military power as a constant deterrent. Consider three examples:

In 1996, Iranian officers supported an attack on a U.S. military barracks in Saudi Arabia, killing 19 Americans.

In 2007, the Islamic Revolutionary Guard Corps orchestrated an attack on a U.S. military gathering in Karbala, Iraq. They killed one American soldier on the spot and executed four others shortly after kidnapping them.

In 2009, the Islamic Revolutionary Guard Corps's Quds Force division plotted to kill Saudi Arabia's ambassador to the United States as he dined at a restaurant in Washington, D.C. Warned that 100 civilians might die, the Iranian operations officer responded "F--- 'em."

This record demands our attention in the present circumstances.

As of this moment, the Iranian hardliners have the aligned motive (hatred and a need to alter the sanctions status quo), authority (Khamenei's harder line), and confidence (a belief Trump is desperate to avoid conflict) to escalate against America. It may be through proxies or Iranian operatives directly, but it is likely that Iran will soon strike American interests.

Trump must again clarify that any attack which harms American citizens will result in military retaliation.