Russian President Vladimir Putin, right, shakes hands with Syrian President Bashar al-Assad during an Oct. 20 meeting at the Kremlin in Moscow. (Alexei Druzhinin/pool/RIA-Novosti via AP)

On Nov. 1, Iran’s ambassador to Russia, Mehdi Sanaei, declared that a “new chapter” in relations between Iran and Russia had begun. As evidence, Sanaei cited progress in bilateral trade relations, a $5 billion line of credit between the two countries, military cooperation in Syria and Russia’s support for Iran’s pursuit of peaceful nuclear energy.

So are Russian-Iranian relations now cheerful and sunny, with nary a cloud in the sky?

Not exactly. Contrary to the opinions of leading analysts, like Brookings fellow Sergey Aleksashenko, the alliance isn’t as strong as the official rhetoric suggests. Three areas of tension trouble the Russia-Iran partnership: a history of distrust between the two nation’s elites, economic cooperation in oil and gas, and seriously clashing ambitions in Syria.

1. There’s a history of distrust between Russian and Iranian elites

 After Iran’s 1979 revolution, the country had a tense relationship with the Soviet Union. The USSR supported Iraq during the Iran-Iraq War (1980-1988), as it feared an Iranian victory would spread Khomeini’s Islamist ideology across the Middle East.

After the Soviet Union collapsed, Russia’s relationship with Iran thawed. Russia expanded commercial ties, sold arms to Iran, and by the mid-1990s was actively helping Iran in the development of its nuclear program. That’s because Iran and Russia shared some geopolitical interests. Both countries opposed Turkey’s strategy in the Middle East and the U.S.’s expanded influence in Central Asia.

But Russia-Iran cooperation polarized each country’s elites because of their long-standing distrust for one another. This animosity stemmed from Iran’s opaque military buildup and Russia’s historic ambitions of enveloping Iran within its sphere of influence. Russian elites saw Iran as untrustworthy; Iranian elites saw Russia as imperial and arrogant.

This distrust showed up in a number of ways. In 1996, Igor Rodinov, Russia’s defense minister under Boris Yeltsin, listed Iran as a country whose military buildup could threaten the post-Soviet region that had recently formed the Commonwealth of Independent States (CIS). A 2003 Ministry of Defense report revealed Russia’s disdain for Iran’s nuclear ambitions, leading Russia to cut assistance to the project.

[Three and a half reasons why Russia might be planning to withdraw from Ukraine–or some of it, anyway]

Vladimir Putin and Dmitri Medvedev took opposite points of view about Iran’s nuclear program. In 2009, Putin denied that Iran had nuclear aspirations while Medvedev said in 2010 that Iran was close to producing a nuclear bomb. That revealed how deeply divided Russian elites were about the credibility of Iran’s nuclear plans. In 2012, Putin expressed concern that a nuclear-armed Iran would destabilize the Middle East — making it clear that Russian support for Iran could evaporate if it developed a nuclear bomb.

In turn, Iran made clear that it opposed Russia’s disapproval, through provocative actions like a 2011 lawsuit against the Russian government over its decision to suspend S-300 missile shipments. Mark Katz, a professor of politics at George Mason University and a noted expert on Russia-Middle East relations, argues that Iran viewed Russia’s insistence that it be Iran’s only supplier of uranium, as an act of imperial hubris. Katz claims that Iranian elites believed that Russia should treat Iran as an equal partner, or even as the superior partner, since Russia was benefiting considerably from its investments in Iran. This notion of equal partnership extends to the ongoing Syria campaign, as Iranian parliament speaker Ali Larijani has emphasized that Russia consulted Iran before launching airstrikes on behalf of Assad.

But if Iranians see Russia as “imperial” while Russians see Iran as “untrustworthy”, diplomatic cooperation will be extremely difficult. Without trust, there’s no durable strategic partnership.

2. Now Russia and Iran are competing

Even though Russia supported United Nations sanctions against Iran in 2010, the Kremlin has been consistently critical of damaging effects on sanctions on the Iranian economy and has emphasized the need for the West to end Iran’s international isolation. So it’s hardly surprising that Russian Foreign Minister Sergei Lavrov enthusiastically praised the nuclear deal.

Russia resumed S-300 missile shipments to Iran, and Moscow’s business community hailed the potential for lucrative contracts in the civilian nuclear energy sector.

[Okay, so what if Iran does get nuclear weapons?]

Despite the trade benefits, the Iran nuclear deal is a net loss for Russia for two reasons.

First, Russia has lost its diplomatic leverage over Iran. That’s the conclusion of Alexei Malashenko, a leading expert in Russia-Middle East relations at the Carnegie Moscow Center, who recently told me that that’s because Russia is no longer needed to mediate between Iran and the West.

Iran has now signed multi-billion dollar trade deals with Europe and with countries in the Asia-Pacific region, which makes Russia less important to Iran. This diversification has not been met with approval from anti-Western hawks in the Kremlin’s inner circle. For example, Deputy Prime Minister Dmitry Rogozin uncharacteristically refused to comment on the nuclear deal.

Second, Iran is now competing with Russia in the global energy markets. Russian economists fear that Iran’s increased production will keep oil prices low for years longer than expected. The Kremlin disagrees, claiming that world markets have already factored in the Iran deal’s impact into their pricing decisions.

But China is now buying Iranian oil. Iran is about to join the Shanghai Cooperation Organization (SCO), a Eurasian political, military and economic organization, linking Russia and China to Central Asia. All that strengthens Iran’s argument that it must be treated as an equal partner with Russia. The Kremlin doesn’t like that; it wants Iran to be a junior partner, not a challenger.

3. Russia and Iran are on a collision course in Syria

Both Russia and Iran have supported Bashar al-Assad’s regime, naming them close allies in the Syrian civil war. But they have drastically different motives for their support–motives that make their cooperation quite unstable.

[When he bombs Syria, Putin is sending these four messages to the world]

Iran supports Assad because it wants to create a Shiite Crescent in the Middle East. If Assad fell, Syria would almost certainly end up with a Sunni-dominated government backed by Iran’s rivals, Saudi Arabia and Qatar.

Assad’s fall would also leave Iran isolated in the Middle East; Iraq would be its only regional ally. Assad is a secular dictator, whose values conflict drastically with those of the Iranian regime’s theocracy. But Iran needs him as Syria’s leader if it wants to be a regional great power.

Russia has a different — although also powerful — stake in Syria: a naval base in Tartus, long-standing arms contracts and few other regional allies. But Russia’s Syrian involvement is based on different geopolitical principles. Russia is trying to protect authoritarian regimes from Western military interventions that violate their sovereignty, and wants a multi-polar world to counter the dominance of American values.

[Hey, Putin, have you seen how much China is investing in Ukraine?]

For Russia, Syria is merely a theater for upholding these larger principles. Russia is significantly less willing to sacrifice human lives than is Iran. Putin’s popularity would take a hit if Russia were dragged into a long war in Syria as it once was in Afghanistan. Unlike Iran, Russia wants to keep trading with Sunni countries opposed to Assad, like Turkey and Saudi Arabia, and can’t afford to make enemies of them. And Russia worries about Iran’s ideological zeal in Syria, fearing that Iran’s Islamic doctrine could spur Russian Muslims to start agitating against the Kremlin. 

Those differences are starting to show. The head of Iran’s Revolutionary Guard, Mohammed Ali Jafari, recently said that Iran cares more about Syria than Russia does. While the recent plane crash in Sinai might increase Russia’s involvement in Syria in the short-term, further terrorist attacks could lead to a Russian retrenchment in the long-term, that would deepen divisions with Iran.

Deep distrust, economic competition and conflicting ideological agendas: Those three tensions make the Russia-Iran alliance quite unstable. These tensions could create a schism amongst the pro-Assad forces in Syria that would embolden ISIS and worsen the chaos created by the ongoing Syrian civil war.

Samuel Ramani is an master of philosophy student in Russian and East European studies at St. Antony’s College, University of Oxford, specializing in post-1991 Russian foreign policy.