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 remain in 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.