Bloomberg View’s Eli Lake and Josh Rogin recently reported that U.S. troops are sharing a base with Iran-backed Shiite militias in Iraq, where Tehran’s notorious proxies are spying on U.S. operations and personnel at their leisure to prepare the ground for future crimes. This worrying revelation is the latest manifestation of a misconception about the Iranian regime’s nature and its intentions in Iraq -- an error that can prove to be fatal if not corrected.

In his interviews with different media outlets, U.S. President Barack Obama has made assertions about the Iranian regime being able to become a successful regional power and help stabilize the Middle East. Also, in his secret missives to the Iranian regime’s Supreme Leader, Ayatollah Ali Khamenei, Obama has promised that in the event of a final accord on Iran’s contested nuclear program, the U.S. is willing to cooperate with Iran in the fight against the Islamic State, an extremist group that is rampaging through the Middle East and has cut itself a caliphate out of territory straddling Iraq and Syria.

The assumption that Tehran can help in the fight to counter the advances of the IS stems from the shortsighted thinking that as a Shiite extremist powerhouse, the Iranian regime is the archenemy of the Sunni extremist Islamic State.

But a quick review of Iran’s actions in recent years proves that Tehran’s foreign policy in the region is not based on ideological tenets, but rather on setting up short-term -- and sometimes contradictory -- alliances to further its ultimate end: keeping the Middle East in a state of instability in order to remain the main power broker and hegemon of the region.

For instance, in 2001, Iran allegedly helped the U.S. with intelligence in invading Afghanistan and defeating the Taliban, a Sunni extremist government which at the time was a rival to the Iranian regime.  But today, Iran is providing training camps to Taliban fighters and is backing it with cash and arms to fight Islamic State and counter U.S. influence in the region.

Another example is Yemen, where Iran’s proxy, the Houthi militants, have cast their lot with Iran’s former bitter enemy, ousted President Ali Abdullah Saleh, and have occupied large swathes of the country, triggering a regional conflict and an all-out humanitarian crisis that is spreading across the Arabian Peninsula.

Iran also has regional goals in Iraq and Syria. While in Iraq, the Popular Mobilization Forces -- an Iran-backed umbrella of Shiite militias -- are ostensibly fighting the Islamic State, in Syria, the embattled regime of Bashar al-Assad, which is backed by a plethora of Iranian proxy militias, is effectively colluding with the Islamic State in order to fend off the advances of opposition forces.

Moreover, Iran has at some point given refuge to the leaders of al-Qaeda in Iraq (AQI), the precursor to the Islamic State, because at the time, doing so served Tehran’s purpose to undermine the U.S.-led effort to restore order in Iraq.

To conclude, Iran’s loyalties are tactical and volatile, and relying on its Shiite nature as a basis for enlisting it in the fight against IS can prove to be calamitous. As soon as Tehran reaches the conclusion that IS is no longer a threat for its regional ambitions, it will order its forces to turn their weapons toward its next rival – the U.S. and its allies in the region. And it should not come as a surprise if Iran decides to align itself with the remnants of IS to that end. 

Ironically, as Lake and Rogin’s report states, among the groups now sharing headquarters with the U.S. advisors in Iraq, some are designated as terrorist groups, and their members openly brag about their past record of murdering U.S. troops in Iraq. They wouldn’t think twice about doing so again, should the need arise. The Iranian regime is notoriously known for exploiting its counterparts’ vulnerabilities in order to strengthen its hand in negotiations, and right now, Obama’s erroneous interpretation of the regime’s intentions is perhaps providing Tehran with a full array, especially if it decides to assume a more confronting posture toward the U.S. in case the nuclear talks fall apart.

Giving leeway to the Iranian regime’s mischief-making for the sake of fighting IS is a self-defeating strategy that is already on its way to becoming an abject failure. Iran-backed Shiite militias are ransacking Sunni townships and villages behind U.S.-led airstrikes, looting and killing with wild abandon and further alienating a Sunni population that can be the key to defeating the IS. Crimes committed by these militia forces are driving a wedge into the Iraqi sectarian divide and are playing into the hands of both the IS and Iran, which happen to be the two sides of the same coin.

Iran’s goals is to seize Iraq for its own, not to stabilize it against terrorist groups. Therefore, any rational approach to putting back the torn pieces of Iraq would first start by the total eviction of the Iranian regime and its terrorist elements from the country. Not doing so will only help embolden Tehran in its evil deeds and increase the Iranian regime’s influence in Iraq and the Middle East.

To marshal Iraqis against the onslaught of the IS, the marginalized Sunni population needs to be empowered with both the political and the military clout needed to take part in reuniting the country and driving out extremist elements.  They have already proven to be capable of doing so during the 2006-2007 surge against al-Qaeda. 

Amir Basiri is an Iranian human rights activist and a supporter of democratic regime change in Iran. He tweets at @Amir_bas