(NEXSTAR) -- On Saturday, Pres. Donald Trump attended the dignified transfer of six U.S. service members killed in Iranian strikes. Their remains arrived at Dover Air Force Base in Delaware one week after the U.S. and Israel launched joint strikes against Iran. The six Army Reserve soldiers, whose ages ranged from 20 to 54, are the first American casualties of the ongoing conflict with Iran. The logistics team was killed in an Iranian drone strike while at a command center in Kuwait last Sunday. Pres. Trump and top military leaders rendered a final salute at the Dover Air Force Base, where he shared his condolences. "A very sad situation, to greet the families of the heroes coming home from Iran, coming home in a different manner than they thought they'd be coming home," said Trump. The president promised to avenge their deaths, and more airstrikes hit Iran's capital city on Saturday. Trump warned that more U.S. casualties are likely. The warning has prompted backlash from Democrats who call the war without congressional approval illegal. Senate Minority Leader Chuck Schumer (D-NY) said a war with Iran is "not what the American people want." But the president is only hardening his stance. On Saturday, he said Iran would be hit very hard in new areas. The goal: complete destruction and certain death. Iran, meanwhile, is apologizing for strikes on neighboring Gulf states, but Iran's president says Tehran will continue to target locations where U.S. attacks originate. The U.S. military has around 50,000 military service members in the Middle East at the moment. Pres. Trump says the U.S. will not retreat until Iran's "unconditional surrender."