Oil prices have risen after US President Donald Trump said Iran's response to US proposals to end the war was "totally unacceptable".
Official Tehran has sent its response through Pakistan, which has served as a mediator between the two sides, demanding an immediate end to the conflict, and guarantees that there will be no further US-Israeli attack on Iran, according to Iran's semi-official Tasnim news agency.
The international price of Brent crude rose 4.1% to $105.50 a barrel in Asian trade, before falling slightly.
The key waterway of the Strait of Hormuz has been effectively closed since the war began on February 28, severely disrupting global oil and gas supplies.
Responding to Tehran's conditions, Trump posted on social media that he did not like Iran's response.
Washington's conditions in the 1-page proposal included restoring free transit through
also
Iran rejects Trump's criticism, says their proposal was 'generous'
Strait of Hormuz and the suspension of Iranian nuclear enrichment, according to the American news agency Axios.
Israeli Prime Minister Benjamin Netanyahu has also said that the war with Iran will not end until its enriched uranium reserves are "taken out of play."
A ceasefire announced in early April to allow time for peace talks has largely been respected, despite occasional exchanges of attacks.
US-Iran standoff pushes up oil prices as Hormuz closure continues
US President Donald Trump's swift rejection of Iran's response to a US peace proposal has added to concerns that the 10-week conflict will drag on and continue to paralyse shipping through the Strait of Hormuz, sending oil prices higher on Monday.
The international price of Brent crude rose 4.1% to $105.50 a barrel, before falling slightly.
Days after Washington presented a proposal aimed at resuming negotiations, Iran on Sunday released a response focused on ending the war on all fronts, including Lebanon, where US ally Israel is fighting Iranian-backed Hezbollah militants.
Official Tehran has also demanded compensation for war damages, to emphasize its sovereignty over the Strait of Hormuz, and has called on the United States to end the naval blockade, guarantee that there will be no further attacks, lift sanctions, and lift the ban on the sale of Iranian oil.
Within hours, Trump rejected Tehran's offer in a post on the social network Truth Social.
"I don't like it — Totally unacceptable," Trump wrote without giving further details.
The United States had proposed a ceasefire before talks began on more sensitive issues, including Iran's nuclear program.
Tehran reacted on Monday by defending its position.
"Our position is legitimate: we demand an end to the war, the lifting of the American blockade, and the release of Iranian assets that have been unjustly frozen in banks due to American pressure," said Iranian Foreign Ministry spokesman Esmaeil Baghaei.
"Safe passage through the Strait of Hormuz and establishing security in the region and in Lebanon were other Iranian demands, which are considered a generous and responsible offer," he added.
The standoff has left the Strait of Hormuz largely closed. Before the war began on February 28, the narrow waterway carried a fifth of the world's oil and liquefied natural gas and has since become a key flashpoint in the conflict.
Disruptions caused by the near-total closure of the strait have forced oil producers to cut exports, and OPEC output fell further in April to its lowest level in more than two decades, according to a Reuters poll.
Traffic through the Strait of Hormuz has been significantly reduced compared to the pre-war period. Shipping data from Kpler and LSEG showed that last week only three crude oil tankers left the waterway, with tracking systems turned off to avoid Iranian attacks.
Sporadic clashes around the strait in recent days have tested the ceasefire that has halted full-scale fighting since it came into effect in early April.
Meanwhile, Washington has faced difficulty securing international support, as NATO allies have refused to send ships to reopen the waterway without a full peace agreement and an internationally mandated mission.
The next diplomatic or military steps remain unclear. Trump is expected to arrive in Beijing on Wednesday, where Iran is expected to be among the topics discussed with Chinese President Xi Jinping.
Iran rejects Trump's criticism, says their proposal was 'generous'
Iran's latest proposal to end the US-Israel war was reasonable and generous, Iranian Foreign Ministry spokesman Esmail Baghaei said on Monday, following its rejection by US President Donald Trump.
"Everything we proposed in our text consisted of reasonable demands, responsible demands and generous proposals - not only for Iran's national interests, but for the good, stability and security of the entire region and the world," Baghaei said during a press conference broadcast on Iranian television.
Trump on Sunday called the proposal from Iran "totally unacceptable."
Tehran's demands included ending the war in the region, ending what Baghaei called "maritime piracy against Iranian ships" and releasing Iranian assets that have been "frozen in foreign banks due to US pressure," the Iranian official said.
Iranian state media has reported that demands in Iran's counterproposal also included recognition of sovereignty over the blocked Strait of Hormuz and compensation for war damages.
"Regarding the continuation of the process, we have shown that despite all concerns, we are focused on Iran's national interests. We will act in any way necessary to secure our interests," Baghaei said, speaking about Trump's opposition to the Iranian plan.