Democratic presidential candidate Pete Buttigieg, a military veteran, on Friday said President Trump's authorization of the attack on Iranian commander Qassem Soleimani "must not be the beginning of another endless war."
Killing of Iranian commander 'extreme provocation': Buttigieg
Iran promised vengeance after a U.S. air strike in Baghdad on Friday killed Qassem Soleimani, Tehran's most prominent military commander and the architect of its growing influence in the Middle East.
Soleimani, a 62-year-old general who headed the elite Quds Force, was regarded as the second most powerful figure in Iran after Supreme Leader Ayatollah Ali Khamenei.
The overnight attack, authorised by President Donald Trump, was a dramatic escalation in a "shadow war" in the Middle East between Iran and the United States and its allies, principally Israel and Saudi Arabia.
U.S. Secretary of State Mike Pompeo said the strike aimed to disrupt an "imminent attack" that would have endangered Americans in the Middle East.
Democratic critics said the Republican president had raised the risk of more violence in a dangerous region.