Washington has defended last week's killing of General Qassem Soleimani, the powerful Iranian commander.
President Donald Trump ordered the US forces to attack and kill the leader of Iran Revolutionary Guard Corps, accusing him of sponsoring terrorism.
In a letter to the United Nations Security Council, the US has defended the death, insisting that they did it for self defense.
U.S. Ambassador Kelly Craft said the United States also stands “ready to engage without preconditions in serious negotiations with Iran, with the goal of preventing further endangerment of international peace and security or escalation by the Iranian regime.
"The killing of Soleimani in Baghdad on Friday was justified under Article 51 of the U.N. Charter, wrote Craft in the letter seen by Reuters, adding “the United States is prepared to take additional actions in the region as necessary to continue to protect U.S. personnel and interests.”
Already, Iran has responded by firing dozens of missiles at US bases in Iraq, although no casualties were reported by Pentagon.
Supreme Leader Ayatollah Khamenei on Monday warned that Iran will "do everything to push the US military out of the Middle East".
Close to one million people attended the Monday's funeral in Tehran. Iran said, "the missile attack is the weakest revenge" among many options we have.