US President Donald Trump said on Monday that a ceasefire with Iran was "on life support" after Tehran's response to a US proposal to end the war made clear the two sides were still far apart on a number of issues.

Iran has called for an end ‌to the war on all fronts, including Lebanon, where US ally Israel is fighting Iran-backed Hezbollah militants. Tehran also demanded compensation for war damage, an end to the US naval blockade, a guarantee of no further attacks, and resumption of Iranian oil sales.

Tehran also emphasised its sovereignty over the Strait of Hormuz, where it has shut down shipping traffic that normally carries one-fifth of the world's oil and gas supply.

Trump said Iran's response threatened the status of a ceasefire that has been in place since April 7.

"I would call it the weakest right now, after reading that piece of garbage they sent us. I didn't even finish reading it," said Trump, who has repeatedly threatened to end the ceasefire.

The US had proposed an end to fighting before starting talks on more contentious issues, including Iran's nuclear program.

Tehran defended its stance on Monday.

"Our demand is legitimate," Foreign Ministry spokesperson Esmaeil ⁠Baghaei said.

Iran's parliament speaker Mohammad Baqer Qalibaf said that Iran's armed forces are ready to respond decisively to any "act of aggression".

Brent crude oil futures were up 3% to more than $104 a barrel, as the deadlock left the Strait of Hormuz largely closed. Before the war began on February 28, the narrow waterway carried one-fifth of the world's oil and liquefied natural gas, and has since become a central pressure point in the conflict.

Disruption caused by the near-closure of the strait has forced oil producers to cut exports, and OPEC oil output dropped further in April to the lowest in more than two decades, a Reuters survey showed on Monday.

The United States on Monday imposed new sanctions on individuals and companies it said were helping Iran ship oil to China, part of efforts to cut off funding for Tehran’s military and nuclear programs, while also warning banks about attempts to evade existing curbs.

Trickle of shipping through Hormuz

Traffic through the Strait of Hormuz is at a trickle compared with before the war. Shipping data on Kpler and LSEG showed that three tankers laden with crude exited the waterway last week, with trackers switched off to avoid an Iranian attack.

A second Qatari LNG tanker was attempting to transit the strait, the data showed, days after the first such cargo crossed under an arrangement involving Iran and Pakistan.

Sporadic flare-ups around the strait in recent days have tested the ceasefire.

In the US, surveys show the war ‌is unpopular with ⁠voters facing higher gasoline prices less than six months before nationwide elections that will determine whether Trump's Republican Party retains control of Congress.

Two out of three Americans think Trump has not clearly explained why the country has gone to war, according to a Reuters/Ipsos poll completed on Monday.

More than two months into a conflict that began February 28 with a US-Israeli bombing campaign, some 66% of poll respondents - including one in three Republicans and almost all Democrats - said Trump has not "clearly explained the goals of US military involvement in Iran."

Iran's Qalibaf seized on the mounting discontent in the US, warning that a prolonged war would deepen the burden on Americans. "The longer they drag their feet, the more American taxpayers will pay for it," he said in his post on ⁠X.

Washington has also struggled to build international support, with NATO allies refusing to send ships to reopen the waterway without a full peace deal and an internationally mandated mission.

Hakan Fidan, the foreign minister of Turkey, which has been liaising closely with the US, Iran and mediator Pakistan since the start of the war, will hold talks in Qatar on Tuesday on the conflict and on ensuring navigational safety in the strait, a Turkish diplomatic source said.

UAE'S attacks

The war is also exposing rifts within the Middle East, with ⁠some US allies taking a more direct role in the conflict. The United Arab Emirates, which has borne the brunt of Iranian counterattacks, has carried out military strikes on Iran, the Wall Street Journal reported on Monday, citing people familiar with the matter.

The strikes, which the UAE has not publicly acknowledged, included an attack on a refinery on Iran's Lavan Island last month, the Journal said. Reuters could not immediately verify the report.

At the time of the April ⁠8 strike on Lavan, the National Iranian Oil Refining and Distribution Company called it an "enemy attack." The next day, Iran's Mizan news agency reported it was carried out by Mirage fighter jets used by the UAE.

Trump is expected to arrive in Beijing on Wednesday, where Iran is set to be among the topics discussed with Chinese President Xi Jinping.