Afghanistan’s top peace negotiator has arrived in neighboring Iran as intra-Afghan peace negotiations are under way in the Gulf state of Qatar.

Negotiators from the Afghan government and the Taliban have been locked in talks since September 12 but have been unable to agree on a framework for the negotiations aimed at ending the 19-year war.

Abdullah Abdullah, the head of Afghanistan's High Council for National Reconciliation, a body that oversees the peace talks with the Taliban, arrived in Tehran on October 18 for a three-day visit.

Iran is a key regional power broker with sway over the Taliban and Afghan political factions.

In a tweet, Abdullah said he would “meet the Iranian leadership” and “exchange views on Afghanistan Peace and all other relevant bilateral issues to promote long-term cooperation & friendship.”

His visit comes after a recent trip to neighboring Pakistan, another regional power and the Taliban’s main sponsor.

The relationship between Shi’ite-majority Iran and the Taliban, a fundamentalist Sunni group, is complex. Iran officially opposes the Taliban, but experts said it provides some military support to the mainstream Taliban and even rival breakaway factions.

Abdullah's visit to Tehran comes after the U.S. special envoy for Afghan reconciliation, Zalmay Khalilzad, said last week that Iran "wants to keep the U.S. in an unwinnable and costly war in Afghanistan."

Under a landmark deal signed between the United States and the Taliban in February, foreign forces will leave Afghanistan by May 2021 in exchange for counterterrorism guarantees from the Taliban, which agreed to negotiate a permanent cease-fire and a power-sharing formula with the Afghan government.