But the first face-to-face meeting between Western and Iranian officials in the weeklong war concluded after four hours with no sign of an immediate breakthrough.
To give diplomacy a chance, Trump said he would put off deciding for up to two weeks whether to join Israel's air campaign against Iran.
Whether or not the US joins, Israeli Prime Minister Benjamin Netanyahu said Israel's military operation in Iran would continue "for as long as it takes" to eliminate what he called the existential threat of Iran's nuclear program and arsenal of ballistic missiles.
As negotiations ended in Switzerland, European officials expressed hope for future negotiations and Iran's top diplomat said he was open to further dialogue.
But Iranian Foreign Minister Abbas Araghchi emphasised that Tehran had no interest in negotiating with the US while Israel continued attacking.
"Iran is ready to consider diplomacy if aggression ceases and the aggressor is held accountable for its committed crimes," he told reporters.
Trump was dismissive of the Geneva talks saying Iran didn't want to speak to Europe.
"They want to speak to us. Europe is not going to be able to help in this," Trump said.
Those comments - however blunt - were not refuted by the Europeans.
"Above all, it is of great importance that the United States of America be involved in these negotiations and in finding a solution," German Foreign Minister Johann Wadephul said after the meeting.
After Israeli warplanes hit dozens of military targets across Iran, including missile-manufacturing facilities, an Iranian missile crashed into Israel's northern city of Haifa, sending plumes of smoke billowing over the Mediterranean port and wounding at least 31 people.
Israel's air attacks since its campaign began on June 13 have killed 639 people in Iran, according to the Human Rights Activists News Agency, a US-based human rights organisation. The dead include the military's top echelon and nuclear scientists.
In Israel, 24 civilians have been killed in Iranian missile attacks, according to authorities.
Addressing an emergency meeting of the UN Security Council, the head of the International Atomic Energy Agency warned Israel against attacks on Iran's nuclear reactors, particularly its only commercial nuclear power plant in the southern city of Bushehr.
"I want to make it absolutely and completely clear...a direct hit would result in a very high release of radioactivity to the environment," said Rafael Grossi, chief of the UN nuclear watchdog.
Israel has instead focused its strikes on the main uranium enrichment facility at Natanz, centrifuge workshops near Tehran, laboratories in Isfahan and the country's Arak heavy water reactor southwest of the capital. Grossi has warned repeatedly that such sites should not be military targets.
Iranian state media reported explosions from Israeli strikes in an industrial area of Rasht, along the coast of the Caspian Sea. Israel's military had warned the public to evacuate the area, but with Iran's internet shut off — now for more than 48 hours — it's unclear just how many people could see the message.
Iran has insisted on its right to enrich uranium — albeit at lower levels — in recent talks over its nuclear program. But Trump, like Israel, has demanded Iran end its enrichment program altogether.
Iran had previously agreed to limit its uranium enrichment and allow international inspectors access to its nuclear sites under a 2015 deal with the US, France, China, Russia, Britain and Germany in exchange for sanctions relief.
But after Trump pulled the US unilaterally out of the deal during his first term, Iran began enriching uranium up to 60 per cent — a short, technical step away from weapons-grade levels of 90 per cent — and restricting access to its nuclear facilities.
with DPA
