Iraqi Prime Minister Nouri al-Maliki

Mr. al-Maliki strove to appease both Iran and the U.S., treading lightly between the two, which are vying for hegemony over Iraq. Speaking June 7 alongside Iranian Foreign Minister Manouchehr Mottaki in Tehran, Mr. al-Maliki pledged that “Iraq will not be used as a military launch pad” against Iran.

The remarks by Mr. al-Maliki come at a time when Iran is becoming ever more suspicious of U.S. intentions toward it, fearing the superpower might consider using Iraq either as a base or a corridor to attack Iran.

But his apparent reassurances to Iran over the contentious security deal can hardly be mollifying to Iranians and perhaps at worst, in their view, denote Mr. al-Maliki’s determination to maintain a strong relationship with the U.S.

Even the defense deal Mr. al-Maliki signed with Iran, which was meant to signify the importance Iraq attached to relations with its neighbor, hardly nears the new agreement with the U.S., which is still being negotiated but was outlined in the Declaration of Principles signed by Iraqi and U.S. leaders late last year. The Declaration of Principles states clearly that the U.S. will protect Iraq in the face of “foreign aggression,” which many say is a code phrase for Iranian intervention in Iraq, as alleged by Washington. Iran is not going to be pleased with that sort of attitude from Mr. al-Maliki, a Shia whom Tehran expects to be more attentive to its concerns in Iraq.

The Iraq-Iran-U.S. triangle is a highly complex and complicated web of relationships.

While Mr. al-Maliki recognizes the importance of having a long-term strategic deal with the U.S., to give the appearance of an Iraq under protection to the neighboring countries, he is very cautious not to go too far with it. As an Iraqi and a Shia, Mr. al-Maliki has tried to deal very carefully with Iran, first, so as not to spark the wrath of the eastern neighbor, which wields a great deal of influence in Iraq, and second, to convince Iran to play a positive role in stabilizing his country. Few people know as well as Mr. al-Maliki does the real extent of Iranian power in Iraq and the consequences if it does not like the future arrangements of the country.

Some of Mr. al-Maliki’s recent moves have raised alarm bells within Iran. The embattled prime minister has ordered military operations to clamp down on anti-government Shia and Sunni forces in places such as Basra, Baghdad and Mosul, with the aim of imposing order and establishing a new reputation for himself as a patriotic, nonsectarian leader.

But the attacks on Shia groups drew Tehran’s ire. Iranian officials publicly warned against their continuation, perhaps fearing the weakening of their influence among Shia militia groups, which are an important tool of leverage in the hands of Iran.

“They accused us of being ungrateful for what Iran has done for the Shiites during Saddam’s rule and of siding with the Americans against Iran,” one Iraqi parliamentarian told the Associated Press in May, discussing what Iranians said during meetings he and other lawmakers had with officials in Tehran.

For its part, while the U.S. wants Iraq to have a relationship with Iran for pragmatic reasons, it certainly does not want Baghdad to lean very far toward Tehran. Washington is comprehensibly outraged by Iran’s attempts to promote its interests across the region, which are not necessarily compatible with those of the U.S., given the current attitude of the two countries toward each other and the serious disagreements they have over major issues in the Middle East, ranging from Israel to Iraq.

All these factors mean that Mr. al-Maliki has to prudently handle the challenge of walking a fine line between the U.S. and Iran.

As the occupying power, the U.S. has more than 150,000 troops stationed on Iraqi soil and enjoys great power and leverage in the country. But being a neighbor, Iran has deep connection with various Iraqi groups, especially Shias and to a lesser extent Kurds. It is thought to be a major beneficiary of the Iraq war.

For Iranian policymakers, Iraq is also a puzzle too hard to unravel at the present. Although Iran has publicly voiced support for Iraq’s stability, it is not willing to contribute much to that stated goal as long as the U.S. is in Iraq. It is more in search of recognition by the U.S. of its role and influence in the Middle East in the first place, which the U.S. has not been ready to publicly acknowledge.

Meanwhile, Iran sees a friendly government in power in its neighbor, which is willing to establish some level of strategic relationship with it. Groups that Tehran used to support in the past, and some up to now, are in power in Baghdad. In theory, a Shia-dominated government in Iraq is expected to expand Iranian influence in the region for the foreseeable future. A stable Iraq offers Iran considerable economic opportunities as well by providing the chance for Iranian businesses to expand and invest in Iraq. The picture goes fine for Iran so far, but at the end, with the U.S. having a strong presence in Iraq, Iranians would not feel comfortable unless they reach some kind of arrangement on their competing roles in the region with the U.S. That is not easy to achieve as long as current attitudes persist—but not impossible, as a recent agreement between Iranian-backed and U.S.-supported factions in Lebanon suggested.

Iran’s concerns about the U.S. presence in Iraq were best expressed by Iran’s Supreme Leader Seyed Ali Khamenei, who bluntly told Mr. al-Maliki that the U.S. was the “fundamental problem” in Iraq.

“The fact that a foreign element wants to interfere in the affairs of Iraq and dominate the country progressively is the main problem for the development and well-being of the Iraqis,” Mr. Khamenei said.