DOVER, Delaware: US President Donald Trump attended a ceremony for four US service members who returned to American soil in flag-draped caskets on Wednesday (Jul 22) after being killed in Iranian attacks in the Middle East.

The ceremony, known as a "dignified transfer" of the bodies, comes amid growing frustration with the US-Israeli war with Iran.

The war has cost US taxpayers at least US$37.5 billion, has led to the deaths of 18 US service members and injured more than 450 troops. It has killed thousands of Iranians.

Both Republican and Democratic lawmakers have raised questions about the war, which has boosted global oil prices and shows no signs of ending. Since the war started in February, Trump has offered differing objectives for the war.

The US president travelled to Dover Air Force Base in Delaware for the ceremony.

"We're going to honour them. For me it's one of the hardest things to do as a president. But it has to be done," Trump said before leaving for the ceremony. Asked what he would tell the families of the fallen, Trump said: "All I'm going to say is, we love you. We love your child, and that's what they are to them. They're their children. There's no games, no nothing."

US presidents, vice presidents and dignitaries regularly attend the solemn transfer ceremonies at Dover - home of the largest US military mortuary - during times of war or conflict.

The three US service members killed when an Iranian missile hit their sleeping barracks at Muwaffaq Salti Air Base in Jordan on Friday were First Lieutenant Tyler James Feehan, 25, Sergeant Angel S. Rampersad, 28, and Private Isabella Gonzales, 19. All three were assigned to US Army air defence brigades.