US President Donald Trump has warned Iran that time is running out to reach a deal to end the conflict, in a social media post that echoed earlier threats against Tehran in a post of his social media platform on May 17.

"For Iran, the Clock is Ticking, and they better get moving, FAST, or there won't be anything left of them. TIME IS OF THE ESSENCE," Trump wrote on his Truth Social platform.

The message came as the American leader was due to speak with Israeli Prime Minister Benjamin Netanyahu on May 17 in what is believed to be a run-up to a potential further attack on Iran, according to Iranian sources.

Iranian media reported that the United States had failed to make concrete concessions in its response to Tehran's latest proposals to end the conflict.

A lack of compromise from Washington would lead to an "impasse in the negotiations", the semi-official Mehr news agency reported.

Trump's post echoed an earlier threat that a "whole civilisation" would die unless Iran agreed to a deal, made shortly before a ceasefire was announced in early April. The president warned earlier this week that the truce was on "massive life support" after rejecting Tehran's demands, which he labelled "totally unacceptable".

Esmail Baghaei, spokesman for the Iranian Foreign Ministry, said Tehran's proposals were "responsible" and "generous".

According to Iran's semi-official Tasnim news agency, the proposals included an immediate end to the war on all fronts, a reference to continued Israeli attacks against Iran-supported Hezbollah in Lebanon, a halt to the US naval blockade of Iranian ports, and guarantees of no further attacks on Iran.

The proposals also reportedly included a demand for compensation for war damage and an emphasis on Iranian sovereignty over the Strait of Hormuz.

The conflict between Iran, Israel and the United States began on February 28, when US and Israeli forces launched strikes against Iranian military, nuclear and energy targets.

A fragile ceasefire took hold in early April after Trump accepted a 10-point Iranian framework as a basis for negotiations, but the truce has repeatedly come under strain.

Washington has called for Iran to dismantle its nuclear programme, which it failed to allegedly extract during an operation near Isfahan in March.

The disruption to the strait, through which roughly a fifth of global oil supply passes, has driven Brent crude prices higher and triggered widespread airspace closures across the Persian Gulf.

Iran has maintained a posture of military readiness since the ceasefire, with officials repeatedly warning of a decisive response should hostilities resume.