Democrats have seized on the deaths of three US troops killed in Iranian strikes to urge Donald Trump to urgently reverse his resumption of the war with Iran amid widespread anxiety over climbing casualties.

Even as US forces launched a 10th consecutive wave of attacks against Iranian targets, concern over the deaths of American service personnel threatened to complicate moves to escalate the conflict, which has reignited after he last week walked away from a memorandum of understanding agreed with Iran in June.

The Pentagon released the names of two soldiers killed in a strike on Muwaffaq Salti air base in Jordan on Friday. They were First Lieutenant Tyler James Feehan, 25, of Ewa Beach, Hawaii, and Private Isabella Gonzales, 19, of Carrollton, Texas.

A third member of the armed forces was killed in northern Iraq on Saturday in what US Central Command called a “controlled detonation” of unexploded ordnance. The remains of a possible fourth dead service member were found over the weekend in Jordan.

Chris Murphy, a Democratic senator for Connecticut, accused Trump of having “frighteningly lost control of this war”.

“For those of us who pay attention to the hour-to-hour pace of the Iran War, things are getting very dark very quickly,” he wrote on social media. “The scale of attacks – and threats of escalation – are increasing rapidly.”

The defense secretary, Pete Hegseth, declared that the US would not be deterred by the casualties, writing: “Godspeed, heroes. Their sacrifice only stiffens our resolve.”

Iran has vowed to carry out retaliatory strikes against US Gulf allies, which it has branded “collaborators” for providing logistical facilities for strikes on Iranian territory.

In a brief telephone conversation with NewsNation, Trump called the deaths “a very sad thing” and said the service members had died “in service of our country”.

But he faced a chorus of calls from Democrats to step back from his belligerent posture even as Republicans remained supportive.

“The reckless and costly war of choice in Iran has been a disaster for the American people,” wrote Hakeem Jeffries, the Democratic leader in the House of Representatives. “May God continue to watch over our troops who have needlessly been put into harm’s way.”

Mark Warner, the vice chair of the Senate intelligence committee and a Democrat from Virginia, said there were “hundreds of seriously wounded” US personnel, and added it was “remarkable” that casualty figures had not been higher.

“This is what happens when you start a war of choice. And as a member of the Gang of Eight, I can say unequivocally there was no imminent threat from Iran,” he told CBS’s Face the Nation.

Chris Van Hollen, a Democratic senator from Maryland who has introduced war powers resolutions aimed at ending the Iran campaign unless it receives congressional approval, posted: “This senseless war should never have been started and it needs to end NOW.”

Jeanne Shaheen, the party’s ranking members of the Senate foreign relations committee, called for a return to diplomacy. “The President must negotiate an end to this disastrous war,” she wrote.

And Ted Lieu, a California representative who has also vocally advocated reining in Trump through a war powers resolution, wrote: “We need Republicans to join us in passing the War Powers Resolution NOW.”

The New York Times reported that Iranian forces carried out three strikes against US military targets in Jordan last week before Friday’s deadly attacks that were not disclosed by the Pentagon. The newspaper said the Pentagon also did not reveal “dozens” of casualties and damage inflicted by the earlier strikes.

The latest casualties brought the number of US service members killed since the start of the war on 28 February to at least 17. More than 1,700 Iranian civilians are estimated to have been killed.

The House and Senate have both passed war powers resolutions – requiring the president to ask for congressional approval after 60 days of hostilities – with the aim of restraining Trump. But the White House has contended that there has yet to be 60 days of continuous fighting because the clock stopped after an initial ceasefire in April, which held, shakily, for several weeks.

Republicans, meanwhile, have remained publicly supportive of Trump – despite poll figures showing support for the war and the president’s conduct of it low and sliding. A Washington Post-Ipsos survey showed approval for Trump’s handling of the conflict at 29% – lower than the 33% backing his stewardship of the economy, which has been buffeted by soaring fuel prices caused by the war.

A statement from New Mexico Republicans mourned the fresh casualties but accused Democrats of trying to exploit them for political reasons.

“No matter how much Democrats try to politicize this, President Trump’s actions in Iran have made our country safer from a terrorist regime that has inflicted death and carnage on millions of innocent people around the world, including Americans,” the party said in a statement.

James Comer, a representative from Kentucky and one of Trump’s staunchest supporters on Capitol Hill, told Fox News that a military response to the service members’ deaths was essential.

“I don’t think anyone would prefer that we have any type of military conflict in Iran, but that’s the world that we live in,” he said. “We have to respond, and we have to respond swiftly and with full force, and that’s what President Trump’s doing.”

Riley Moore, a West Virginia Republican, told Fox that the “precision” of the strikes on the Jordanian base suggested Iran was receiving targeting information from Russia or China. He called on the US’s Gulf allies on the Gulf Cooperation Council (GCC) to help.

“Where do we go from here is also looking at how we’re going to work with those GCC partners in the region because this could tip over … into a regional destabilizing conflict,” he said.