It is reported by Reuters with reference to the document.
The letter notes that the purpose of the negotiations is "to prevent a further threat to international peace and stability or escalation by the Iranian regime."
Previously, the head of the Pentagon, Mark Esper, said that Iran launched 16 ballistic missiles at US military bases in Iraq from at least three positions, 12 of them hit the target. According to him, 11 missiles hit the Ain al-Assad airbase, another - the base in Erbil, the helicopter, tents and parking lots were damaged.
The missile attack was a response to the January 3 assassination of the Iranian Islamic Revolutionary Guard Corps Kassem Suleimani.