Taliban’s return in Afghanistan poses a balancing act for Iran

For years, Iran has supplied Taliban insurgents with weapons and money, according to U.S. officials, forming an unlikely but resilient bond between Tehran’s Shiite leaders and the fiercely Sunni fundamentalist insurgent group in Afghanistan.

Tehran’s objectives are twofold: to ensure that security and economic ties remain strong—Iran and Afghanistan are important trading partners—and to prevent a flood of refugees across the border.

That challenge comes at a time when other powers, chiefly China, Pakistan and Russia, might also be well-placed to extend their influence in Afghanistan now that the U.S. is leaving.

“Iran wants a stable, friendly Afghanistan that doesn’t pose a threat, and with which it has aligned strategic objectives in favor of the resistance against U.S. and Western influence," said Andrew Peek, a former deputy assistant secretary of state for Iraq and Iran who also served as an adviser on intelligence and special operations issues for Gen. John Allen in Afghanistan.

An early indication of whether Iran will be able to work with the Taliban will be whether Afghanistan’s new rulers allow extremist Sunni terrorist groups to take root there, as al Qaeda did in the 1990s, a development that would pose a threat to Shia Iran and Shias in Afghanistan.

Before the U.S.-led invasion of Afghanistan in 2001, Iran and the Taliban regime were bitter foes. They nearly went to war in 1998, after the Taliban killed 10 Iranian diplomats. Tehran later cooperated with the U.S. in toppling the Taliban, with the two sides sharing intelligence about Taliban and al Qaeda locations. After the Taliban’s ouster, Iran assisted in forming a new Afghan government, bringing together feuding warlords.

A promising sign from Tehran’s perspective came Thursday. In an attempt to portray itself as more tolerant of the country’s Shia minority, Taliban commanders in the northern city of Mazar-I Sharif allowed processions to go ahead to commemorate Ashura, the most important holy day for Shias.

Yet this week the Taliban also destroyed a statue of Abdul Ali Mazari, a leader of the Hazara ethnic minority who died in 1995. “It’s really a dangerous warning for Hazaras," one Kabul-based journalism student said. “Today this statue, next, Hazara people."

Given the history between the two countries, Iran would have preferred a political settlement in Afghanistan that didn’t leave the Taliban as the sole rulers. Iranian officials had called for a responsible withdrawal of U.S. troops, rather than the swift exit they have demanded in Iraq, said Aniseh Bassiri Tabrizi, an expert on Afghan-Iranian relations with the London-based Royal United Services Institute think tank.

“They fear developments similar to the 1990s," Ms. Tabrizi said. “There could be a confrontation between the two."

Following the U.S. invasion of Afghanistan, relations between the Islamic Republic and the Taliban improved, while Iran also pushed back against the American presence across the Middle East. Significantly, Iran strengthened links to the Haqqani network, a hard-line and fiercely anti-Western wing of the Taliban, which has grown increasingly potent over the past decade.

Around 2015, improvised explosive devices that were the hallmark of hard-line Shia militias in Iraq a few years earlier became more commonplace in Afghanistan, likely as a result of Iranian support for the Taliban, Mr. Peek said.

The Taliban have also tried to broaden their support abroad. In the years immediately following the U.S. invasion, the Taliban relied heavily on Pakistan, which allowed Taliban fighters havens where they could regroup. But as the Taliban captured more territory in Afghanistan, the group set up a de facto capital in Sangin in Helmand province, where Taliban commanders had closer ties to Iran.

This week’s upheaval provides Iran with a chance to expand on those ties, and in recent weeks it has been preparing the ground for a closer relationship, to better control the potential chaos in Afghanistan.

In July, Iran hosted delegations from the Afghan republic, represented by former Vice President Yunus Qanuni, and the Taliban’s chief negotiator Mohammad Abbas Stanikzai. On Monday, new Iranian President Ebrahim Raisi refrained from criticizing the Taliban for the chaos unfolding in Kabul and instead pitched the group’s victory as a way forward out of years of war.

“The military defeat and withdrawal of the U.S. from Afghanistan is an opportunity to restore life, security and lasting peace to the country," he said.

Mr. Raisi also spoke with Chinese President Xi Xinping by telephone Wednesday. Iranian state media reported him as saying Iran was willing to collaborate with China to secure stability in Afghanistan.

Still, Iran has concerns about how the situation in Afghanistan will develop, especially if its economy collapses.

Iran already hosts around three million Afghans, among them roughly one million refugees and two million undocumented migrants, according to the United Nations. Iran closed several border crossings with Afghanistan after they were captured by the Taliban in recent weeks and has bolstered its armed forces along its eastern border.

Iran is also Afghanistan’s largest commercial partner, with about $2 billion in bilateral trade each year, nearly one-third of Afghanistan’s total trade volume. Fuel has become an increasingly important commodity, and Iran now exports around 1 million tons legally to Afghanistan in addition to about 1.5 million tons exported illegally, according to David Mansfield, an independent socioeconomist and Afghanistan expert.

In addition to those flashpoints, Iran has long been locked in a water war with Afghan authorities to secure water flow to eastern Iran.

Iran is one of the region’s most water-deficient nations. From 1998 to 2001, the previous Taliban regime closed the sluices at Kajaki dam in Helmand, cutting off the flow of the Helmand River to Iran.

More recently, Iranian-backed fighters have attacked another dam project in Nimruz province, on the Helmand River that would divert water for irrigation and to power a hydroelectric plant, according to Afghan security officials in the province. The Kamal Khan dam was inaugurated earlier this year.

—Ava Sasani contributed to this article.