Revolutionary Guard General Qassem Soleimani, centre, attends a meeting in Tehran in 2016. File picture: Office of the Iranian Supreme Leader via AP

Baghdad — Iran’s Supreme Leader Ayatollah Ali Khamenei has warned that a “harsh retaliation is waiting” for the U.S. after the airstrike on Baghdad airport that killed Iranian Gen. Qassem Soleimani, the head of Iran’s elite Quds Force.

The Iranian state TV carried a statement by Khamenei also calling Soleimani “the international face of resistance.” Khamenei declared three days of public mourning for the general’s death.

The United States killed Iran’s top general and the architect of Tehran’s proxy wars in the Middle East in an airstrike at Baghdad’s international airport early on Friday, an attack that threatens to dramatically ratchet up tensions in the region.

The targeted killing of Gen. Qassem Soleimani, the head of Iran’s elite Quds Force, could draw forceful Iranian retaliation against American interests in the region and spiral into a far larger conflict between the U.S. and Iran, endangering U.S. troops in Iraq, Syria and beyond.

The Defense Department said it killed Soleimani because he “was actively developing plans to attack American diplomats and service members in Iraq and throughout the region.” It also accused Soleimani of approving the attacks on the U.S. Embassy in Baghdad earlier this week.