Ever since the unfolding of the Ukrainian crisis in February, there have been regular news reports suggesting various gas sources that might "displace" Russia as the supplier of two-thirds of Europe's natural gas. Buoyed by steadily progressing negotiations over nuclear power and the prospect of an easing of sanctions, the latest candidate has been Iran.

But is the West really ready to trade one uneasy alliance for another for the sake of energy security?

Gas powerhouse

Russia and Iran both have the potential to be natural gas powerhouses. According to BP's latest annual statistics review, Iran has proven natural gas reserves of 33.8 trillion cubic metres (tcm) and Russia is not far behind with 31.3 tcm. Between the two, they hold 35 percent of total global reserves. The South Pars gas field, which Iran shares with neighboring Qatar, is the world's largest.

But when we look at current production levels, the "displacement" of Russia by Iran as a gas supplier in the short to medium term starts to look like fantasy. In 2013, Russia produced 605 billion cubic meters (bcm) while Iran, constrained by sanctions, modern technologies and investment opportunities, produced little more than a quarter of that figure — 166 bcm. Russia exported a volume almost equal to that (162 bcm) to European countries alone last year.

The Persian Pipeline

Production aside, after several decades of ignoring each other, Iran and Europe do not have the infrastructure to support large-scale gas exports. The current Ankara-Tabriz pipeline into Turkey has a maximum capacity of only 14 bcm.

Already under discussion for several years, the grandly named 3,300-km Persian Pipeline (or Iran-Europe pipeline) is Iran's bid for a place in the Southern Corridor project to import gas to Europe, bypassing Russian territory. The route is now envisaged to cross into Turkey at the border city of Barzagan before reaching Italy, where it would fork into a northern and southern branch, taking gas to either Switzerland, Austria and Germany, or France and Spain.

The politics

But these are technicalities. How we answer the question of "Really, Iran?" is the bigger challenge. The regearing of gas production and transport infrastructure requires long lead times and enormous investments.

Consequently, energy relations tend to be built on sustainable long-term political and economic partnerships with states that importer nations can trust with the energy security of their citizens. Azerbaijan, the current lead supplier for the Southern Corridor project, has been working on its strong alliance and mutual trust with Europe over the last two decades.

The roots of the mutual distrust between Iran and the West — the United Kingdom in particular — lie in the history of Iran's oil and gas sector over the last century. While the Anglo-Iranian Oil Company (now BP) dominated since it obtained its first license in the country in 1913, it saw its assets stripped when the industry was nationalized in 1951 by new reformist prime minister Mohammed Mossadegh.

The coup that followed in 1953, backed by Britain's MI6 and the CIA, and their reinstatement of their ally Shah Pahlavi, gave birth to the surge of hostility toward meddling foreign powers, which ultimately led to 1979's Islamic Revolution. The new Constitution of Iran and the Petroleum Law, which came into force in 1987, banned all kind of foreign investment in the ownership of energy reserves, meaning concessions and the like.

As Iran's forced isolationist policy began to bite, legislative changes made in 1994 tentatively opened up some of Iran's oil and gas sector to IOCs, on the basis of service contracts. But in a country where the impact of the events of 1953 run deep, the anti-Western hardliners still hold sway.

Rouhani the moderate

Although Iran is certainly a procedural democracy rather than a liberal one, it has enviable democratic institutions compared to many of its neighbors. The election last year of Hassan Rouhani, seen as a moderate among radicals, was met with much optimism. This was a man Western leaders could trust, the media announced — newspapers cling onto superficial signals of Iran's "opening up," such as the decision to take down some of Tehran's anti-American posters.

Rouhani has been given significant scope to make progress on domestic and social issues in the name of reviving an ailing, sanctions-battered economy. But on the big-hitting issues of foreign policy and international relations, another man has the final say. Ali Khamenei, Iran's 75 year old Supreme Leader, is the figure seen as providing divine guidance to Iran, and all key decisions must go through him.

In every concession to the West, be it a phone call with Obama or compromises in nuclear negotiations, the new president faces the ire of the conservative factions of Iran's leadership. Those factions came out onto the streets last November, just months after his election, to stamp on the American flag and chant "death to America."

On a rhetorical level, Rouhani still lays the blame for Islamic extremism firmly at the doors of the U.S., as he made clear in his recent speech at the United Nations. To the dismay of the U.S., he has also spoken openly of the need for solidarity between sanctioned nations, striking deals with Russia that undermine U.S. diplomatic efforts.

Iranian politics, a complex web of democratic and theocratic structures, can lead to contradictory signals to would-be Western partners. Iran's partial liberalization is heartening but fragile — born out of necessity, if not desperation. Until trust is restored between Iran and the West, Iran must be treated as a partner of necessity, not a strategic one.

If Iran is "opening up," we must also consider that it has the right to open its gas fields to China, India, Russia, Europe, the U.S. or any other partner that knocks at its door. The Iranians have an incentive to provide gas to a high-demand European market, if for nothing else because of the leverage it allows them in nuclear talks.

But there will be no return to the days of Anglo-Iranian Oil when British oil tankers enjoyed queue-jump rights in Iran. As a poet friend of Khamenei's reminds us, "I will never forget that we were a flame and they doused us with water."

The Russia lesson

It is Rouhani, in fact, who has provided the voice of reason. He told Russian journalists that "today's conditions are not such that if Russia stops selling gas to Europe, Iran can serve as an alternative for Russia's gas exports to those countries" He added that "interaction and healthy competition among gas-exporting countries will serve the interests of all countries."

When Russia withdrew its gas supplies from Ukraine, European leaders learned a harsh lesson about dependence on an unpredictable political power.

Despite impressive reserves, it is fantasy to believe that Iran can "displace" Russian gas in Europe in the medium term. Nor would that be desirable, given that relations between Iran and the West have only been creeping back on track over the course of the last year.

If the U.S. and Europe can also commit to trust-building measures, what Iran does provide is promise, alongside multiple other sources, of another vector in a more diversified and responsible European energy policy.