US Defense Secretary Ashton Carter landed in Jordan Tuesday and met American troops stationed there and colleagues of a Jordanian pilot burned alive by ISIS.
Carter is on the second leg of a regional mission to try to reassure Washington's allies over the nuclear deal between major powers and Iran, but was not scheduled to hold talks with Jordanian officials on that subject.
He met US forces stationed in Jordan and comrades of Jordanian Lieutenant Maaz al-Kassasbeh, who was captured in December after his plane was shot down during a mission over Syria.
In a video two months later, ISIS showed Kassasbeh standing in a cage, where he was doused with fuel, set on fire and left to burn to death.
Kassasbeh's murder caused global revulsion and vows of international efforts to combat the Sunni Muslim extremist group.
"The enemy has to be defeated," Carter told a small group of US mechanics beside an American F-16 in a hangar at the base.
"It will be, because the barbarians are always defeated by civilization, a few by the many."
He later had a private meeting with pilots taking part in anti-ISIS coalition sorties.
Carter is scheduled to travel on to Saudi Arabia on Wednesday.
Earlier Tuesday, he met Israeli Prime Minister Binyamin Netanyahu, a fierce critic of last week's nuclear accord between Tehran and world powers.
Israel and other critics of the deal warn that the expected lifting of sanctions under the agreement will allow the Islamic republic to boost support for terrorist groups and sectarian proxies throughout the Middle East and beyond.
AFP contributed to this report.