TOKYO -- Iranians were jubilant when the U.S. and the European Union lifted the sanctions that had devastated their country.
But not everyone shares their joy.
On the opposite shore of the Persian Gulf, Saudi Arabia is eyeing the developments in Iran with a cold eye. The leadership in Riyadh is increasingly concerned that as the Iranian economy gets back on its feet, so, too, will Tehran's ability to exert its influence throughout the region.
Conflict between Sunni-majority Saudi Arabia and predominantly Shiite Iran has repercussions for the wider world. Adding to an already volatile situation, the U.S. is reducing its engagement in the Middle East, while Russia and China are looking to flex their trade and diplomatic muscles there.
Money to burn
When Ali Tayyebnia, Iran's economic minister, visited Tokyo to sign an investment treaty with Japan recently, he was optimistic about his country's growth prospects. "Iran will seek 8% growth" in real gross domestic product over the next five years, he told the Nikkei Asian Review. Most of that growth will come from expanded oil exports. What Iran's neighbors want to know is how the country will spend its money.
Saudi Arabia suspects that Iran, in addition to investing in domestic industries, may also be aiming to funnel cash into Shiite forces beyond its own borders.
"If this proves anything, it proves that Iran is keen on extending its influence over the countries of the region," Mohammed bin Salman, Saudi Arabia's deputy crown prince and defense minister, said in an interview with The Economist of the U.K. Salman is the son of King Salman bin Abdulaziz, and his remarks are seen as an indication of the royal family's growing alarm.
The two countries differ ethnically as well as religiously. The majority of Iranians speak Persian, and more than 90% of its population is Shiite. Saudi Arabia is ethnically and linguistically Arab, and more than 70% of its people are Sunni.
Saudi Arabia's leaders claim their country is the global leader of the Muslim world because it has the two holiest sites connected with the Prophet Muhammad. But Iran, with a population three times that of Saudi Arabia, has a strong military and, in the 1980s, showed signs of expansionary ambitions.
The Saudi government has taken every opportunity to keep Iran in check.
Tensions escalated sharply this January when Saudi Arabia severed diplomatic relations with Iran. The standoff began with Saudi Arabia's execution of Nimr al-Nimr, a prominent Shiite cleric who lived in the kingdom's Eastern Province, on charges of sedition. Enraged by the execution, young protesters in the Iranian capital raided the Saudi Embassy. Accusing the Iranian government of being behind the attack, Saudi Arabia wasted no time in cutting diplomatic ties.
The speed with which Riyadh reacted to the protests led some in diplomatic circles to suspect that Saudi Arabia had anticipated the unrest the cleric's execution would cause and went ahead with it in order to have an excuse for breaking off ties.
Saudi Arabia is not the only Arab nation concerned about Iran's re-emergence into the world economy. King Abdullah II of Jordan referred to the dangers of the "Shia crescent," an emerging alliance of Shiite forces in the region, centered on a resurgent Iran. The king voiced concern that Iran will use its influence in neighboring countries, such as Iraq, Lebanon and Syria, to revitalize Shiite forces there and eventually pit them against Sunni-led governments.
The enormous religious diversity in these countries provides fertile ground for divisions and conflict. Lebanon, which is often described as a "mosaic of religions," is home to the militant organization Hezbollah. Hezbollah has received money and weapons from Iran, and Tehran has even sent military advisers from the elite Islamic Revolutionary Guards.
Israeli leaders are worried that Iran, now free of economic sanctions, may step up its support of Hezbollah, whose clashes with Israel are seen as an indirect demonstration of Tehran's influence.
Iran counts the regime of Syrian President Bashar al-Assad as a key ally. Assad belongs to the Alawi sect of Shiite Islam, and for two generations his family has held on to power by means of violence and terror.
Their shared Shiite beliefs have been a key factor in Iran-Syria ties, and some observers expect that as its economy improves, Iran will increase its support for Assad. If the beleaguered regime regains its strength, it would be difficult to achieve the scenario envisioned by the U.S., namely, securing stability by ousting Assad.
Strife between the two branches of Islam is also intensifying in Iraq, which is located between Saudi Arabia and Iran. Violence between Sunnis and Shiites there reached new levels after the U.S.-led coalition forces withdrew following the downfall of the Saddam Hussein government in the Iraq War.
In 2013, the Islamic State militant group, which had retreated into Syria to escape from U.S. forces, moved to occupy Iraqi oil fields located in areas gripped by political turmoil. As a result, the group's sphere of influence now straddles the territories of Syria and Iraq. To counter the Islamic State threat, the Iraqi military asked for help from Iran, which has vast experience in military strategy and troop operations. In response, Iran has sent an advisory group from the Islamic Revolutionary Guards to command Iraqi militias as "advisers."
Saudi Arabia is becoming jittery about all this, and its mounting anxiety was likely a large part of the reason for Riyadh's hasty decision in January.
Looking at the broader context, the intensifying row between Saudi Arabia and Iran has much to do with the recent shift in Washington's Middle East strategy.
The relationship between the U.S. and Saudi Arabia has long operated on something of a quid pro quo basis, in which the Saudis maintain stable oil supplies and in return the U.S. provides military support to protect the kingdom from foreign enemies.
Then, a few years ago, the shale revolution came along and the U.S. began producing vast amounts of its own oil. With oil self-sufficiency looking like a viable possibility, America seems to be rethinking its relationship with Saudi Arabia. What's more, in a bid to put greater pressure on an increasingly assertive China, the administration of President Barack Obama has shifted the focus of its military and diplomatic strategy away from the Middle East and toward the Asia-Pacific.
The possibility that the U.S. might reduce or even end its support for Saudi Arabia is a frightening one for Saudi leaders.
Their alarm only intensified as the U.S. grew closer to Iran. In 2013, the U.S. and five other countries reached a broad agreement with Tehran over its nuclear development program. Though the agreement was far from comprehensive, its core part was worked out in secret between Washington and Tehran. These talks helped forge communication channels between the two governments at ministerial levels.
The six countries reached a final agreement with Iran in 2015 and reaffirmed the lifting of the sanctions in January this year. Saudi Arabia's leaders have watched all these developments with a mix of jealousy and alarm.
Russia and China, meanwhile, are aiming to exploit the vacuum created in the Middle East by Washington's shift in geopolitical focus. Moscow and Beijing have promised to cooperate with Tehran in the development of nuclear technology for peaceful purposes. Russia, keen to increase its arms sales to the country, has also clinched a deal to export surface-to-air missile systems to Iran.
China and Russia are eager to tap Iran's economic potential, but it is far from certain that either country can fill the void left by America's waning influence and help maintain world stability.
With world powers unable to stem regional conflicts, the danger that the situation in the Middle East will spiral out of control is frighteningly real.