Ahead of the signing ceremony, US Secretary of State Mike Pompeo had warned Iran against trying to scuttle the agreement. "There is a history of Iran engaging in activity inside of Afghanistan to act as a spoiler," Pompeo said.
In its statement, Iran called for the withdrawal of foreign troops from Afghanistan, saying their presence "is illegal and is one of the main causes of the war and insecurity in that country". Iran said a lasting peace deal could "only be achieved through inter-Afghan dialogue with the participation of all political groups, including the Taliban, and taking into account the considerations of neighbouring countries."
It added: "We believe that the United Nations has the capacity to facilitate negotiations among Afghans and to monitor and ensure the implementation of agreements reached."
Tensions have sharply escalated between Tehran and Washington since May 2018, when US President Donald Trump withdrew from a deal that gave Iran relief from sanctions in return for curbs on its nuclear programme. The arch enemies have appeared to come to the brink of an all-out confrontation twice since then.