As Western forces exit Afghanistan, Iran is watching with alarm. The resolution of one long-standing aim, the withdrawal of U.S. troops, is unleashing a separate challenge: what to do about the Taliban, another longtime problem for Iran, swiftly regaining power and territory next door.
The Afghan government said Friday that the Taliban had captured a key border crossing between Iran and Afghanistan.
Iran, ruled by Shiite clerics, and the Taliban, a radical Sunni movement, are at fundamental odds, and Iran has long bristled at the Taliban's treatment of non-Sunni minorities.
Tehran fears both Taliban rule and Afghanistan returning to civil war, a destabilizing prospect likely to imperil the country's ethnic Persian and Shiite communities, send more waves of Afghan refugees across the border and empower Sunni militancy in the region.
Seeking an upper hand, Iran has cultivated ties with some Taliban factions and softened its tone toward the extremist group, which it sees as all but certain to seize power.
That gamble has elicited fierce debate in Iran, where the repressive Taliban is viewed unfavorably and skepticism of U.S. intentions runs high, even as the Biden administration makes slow headway in talks to return to the 2015 nuclear deal, from which then-President Donald Trump withdrew.
"Iran is going to be harmed immensely by chaos and civil war in Afghanistan," said Fatemeh Aman, a nonresident senior fellow at the Middle East Institute, citing in particular Tehran's fear of the Islamic State's Afghanistan affiliate gaining ground. "They see partial rule as the best-case scenario, with the Taliban in power."
But Iran's increasingly public overtures to the Taliban "could be a miscalculation," said Aman, as "Iran believes they are using the Taliban, but some could argue that the Taliban is using Iran to present themselves as more powerful, worthy of ruling a country."
Iran was excluded from U.S.-Taliban talks in Doha, Qatar, which last year led to a troop withdrawal deal to end two decades of U.S. military operations in Afghanistan. Biden set a Sept. 11 deadline, but the U.S. military said last week that the exit was more than 90% complete.
The Taliban, thought to control around a third of Afghanistan, has so far largely gained ground without full-scale fighting and has instead relied on cutting deals with local leaders.
Still, more than 1,500 Afghan soldiers fled across the border to neighboring Tajikistan in recent weeks to escape Taliban advances, while some 200,000 Afghans have fled their homes this year.
The Taliban's fast-paced advances have left Tehran fearing the possibility that the Taliban could retake Kabul -- but even more so the specter of widespread violence emboldening the flow of extremists, narcotics and weapons, said Aman.
In recent weeks, some Iranian hard-liners -- aligned with Iran's supreme leader, Ayatollah Ali Khamenei, and President-elect Ebrahim Raisi -- have gone on the offensive and publicly painted a rose-tinted picture of a changed Taliban.
In late June, the ultraconservative Kayhan newspaper, tied to the supreme leader, declared, "The Taliban today is different from the Taliban that beheaded people."
Kayhan argued that the Taliban's recent gains have not involved "horrible crimes similar to those of the Islamic State in Iraq," and noted that the Taliban have even said that they have no issues with Shiites.
Some hard-liners rejected this conciliatory take. Recently, the front page of conservative newspaper Jomhouri Eslami criticized Iranian leaders for playing down the threat of "Taliban terrorists" along Iran's border.
On Persian-language social media in Iran and Afghanistan, others condemned Iran's leaders over perceived efforts to whitewash the Taliban's bloody history of attacking Hazaras, a Shiite minority, and repressing women and personal freedoms.
While "the Iranians do care about Afghanistan ... there is no clear strategy for how they are going to handle it," said Vali Nasr of the Johns Hopkins School of Advanced International Studies.
Even before the Doha deal, Iran cultivated ties with Tehran-friendly Taliban factions, as Afghanistan's other neighbors, especially Pakistan, have done for decades.
Iran's long-simmering Taliban ties have become increasingly public. In 2016, a U.S. drone strike killed Taliban leader Mullah Akhtar Mohammad Mansour as he returned to Pakistan after a stay in Iran. In the most high-level meeting between the parties, senior Iranian officials hosted a Taliban delegation in Tehran in late January.
Iran and the United States, however, have in the past found common ground around fighting the Taliban.
As the United States prepared to invade Afghanistan in 2001, Iran, then led by reformist President Mohammad Khatami, provided intelligence. Then-Quds Force commander Qasem Soleimani reportedly oversaw the contact.
After the Taliban fell, Iran continued to help build a new Afghan government and mediate among warlords filling the security void.
But that cooperation ended in January 2002, when President George W. Bush named Iran, North Korea and Iraq an "axis of evil," offending Tehran.
Now, Aman said, Washington and Tehran have a small window of time to cooperate again in Afghanistan's interest.