Iran has increased its support for the Taliban by allowing the militants to open an office in the country while considering the supply of surface-to-air missiles, according to Afghan and Western officials.
By helping the Taliban, Iran aims to derail a decade-long “strategic partnership” signed 
between Afghanistan and America in April. Tehran would also have the option of stirring violence in Afghanistan in retaliation for any US strike on its nuclear facilities.
A member of the Taliban’s “Shura”, or ruling council, was allowed to set up an office in May in the eastern Iranian city of Zahedan. Two months later, intercepted communications showed members of the Quds Force of Iran’s Revolutionary Guard Corps discussing plans to send surface-to-air missiles to Afghanistan, although there was no evidence of the weapons actually being dispatched.
If they were given to the Taliban, this would mark a significant escalation of Iranian support. Iran’s Shia regime was an enemy of the Sunni Taliban when the latter ruled most of Afghanistan between 1996 and 2001. When Taliban forces captured the city of Mazar-i-Sharif in 1998, they murdered nine Iranian diplomats.
However the US was now seen as “the bigger enemy” a Western official in Kabul told the Wall Street Journal. “Iran is willing to put aside ideology and put aside deeply held religious values for their ultimate goal: accelerating the departure of US forces from Afghanistan,” he said.
Nato commanders say Iran has long provided small arms and training to the Taliban. William Hague, the Foreign Secretary, last year complained to Tehran after British SAS soldiers seized a convoy carrying Iranian-manufactured 122mm rockets destined for the Taliban.