Washington: In a concerning development, US President Donald Trump on Monday said the ceasefire with Iran was at its "weakest" and on "massive life support", a day after he rejected Tehran's proposal to end the months-long war.

"It is at its weakest. After reading that piece of garbage they sent us... It's on life support, massive life support," Trump told reporters at the Oval Office in response to a question on the ceasefire with Iran in the wake of the rejection of the peace proposal.

"They think that I'll get tired of this, or I'll get bored, or I'll have some pressure, but there's no pressure, there's no pressure at all. We're going to have a complete victory," Trump said.

Trump received the Iranian proposal on Sunday amid hopes that it could lead to a breakthrough to end the war with Iran that began on February 28, blocking the key sea route for global oil supplies, leading to fuel shortages in several countries.

"I have just read the response from Iran's so-called Representatives.' I don't like it," he wrote on his Truth Social platform on Sunday, calling it "totally unacceptable".

The US and Israel's war on Iran started on February 28, and attacks have been paused since April 8, when the warring sides agreed to a ceasefire.

The US and Iran have been negotiating a deal to end the hostilities for good, but peace has been elusive so far.

The US has been insisting that Iran give a clear commitment to end its uranium enrichment programme in exchange for the lifting of sanctions and release of billions in frozen Iranian funds.

The negotiations also entail both Iran and the US lifting the blockade of the Strait of Hormuz, a key passageway for one-fifth of the global crude supplies. PTI