The airstrikes came just hours after an attack killed and wounded American and British servicemen at a base north of Baghdad.
The attack targeted the Iranian-backed Shia militia in Iraq, marking a major escalation in U.S.-Iran tensions.
The speech offers a preview of how the progressive senator will battle the moderate in a two-person race.
President Donald Trump initially said no Americans were injured in the retaliatory missile strikes on Al-Asad air base in Iraq.
Hundreds of anti-government demonstrators flooded the streets of Baghdad and Iraq's southern provinces on Sunday.
The Pentagon announced that 34 U.S. troops have been diagnosed with traumatic brain injuries after the Iranian missile strike.
The Iranian strike took place Jan. 8 on an air base in Iraq.
The "million-man" march was called for by an influential Shiite cleric, though their numbers fell short of a million.
Soleimani thought he was untouchable, and for more than a decade he was.
At least 11 U.S. service members were airlifted out of Iraq following Iran's missile strikes on the Ain al-Asad air base.