Donald Trump has said the ceasefire with Iran is on “life support” and that he is considering restarting US navy military escorts of ships through the strait of Hormuz in an attempt to end the Iranian blockade of the vital waterway.

The US president dismissed Iran’s peace proposals as stupid, and denied he was under any domestic pressure to reach a deal.

Referring to the ceasefire in force since 7 April, Trump said: “I would call it the weakest, right now, after reading that piece of garbage they sent us – I didn’t even finish reading it.

“I would say the ceasefire is on massive life support, where the doctor walks in and says: ‘Sir, your loved one has approximately a 1% chance of living.’”

Last week, the US sent Iran a set of conditions for easing the conflict, mostly related to preventing Tehran from being able to expand its nuclear programme. At the weekend, Iran sent counter-proposals that Trump dismissed out of hand.

Trump called off Project Freedom, the plan to escort oil tankers through the strait, after little more than two days last week – ostensibly to give Iran time to respond to his peace proposals. The plan for the military escort had also met resistance from Saudi Arabia, which said it would not allow its airspace or bases to be used to support something it regarded as escalatory.

Trump’s latest comments came after oil prices jumped again when Iran said there would be no further talks about ending the blockade of the strait of Hormuz unless he accepted its terms.

Maj Gen Mohammad Ali Jafari, a former commander of the Islamic Revolutionary Guard Corps, said: “As long as the war on all fronts is not over, sanctions are not lifted, blocked funds are not released, war damages are not compensated and Iran’s sovereignty over the strait of Hormuz not recognised, there will be no other negotiations.”

Esmail Baqaei, the Iranian foreign ministry spokesperson, said Iran’s proposals were “reasonable, responsible and generous”. He claimed it was still possible for the two sides to reach agreement, and that nothing Iran had proposed was unreasonable.

Mostafa Taheri, a member of the Iranian parliament’s industry commission, claimed the revenue from the proposed new transit fees for the strait of Hormuz would be worth $15bn (£11bn) annually, about a third of the revenue Iran currently receives from its oil sales, and enough to stabilise foreign exchange reserves.

Oil prices rose to more than $105 a barrel as the deadlock continued, and unpalatable military options that are unlikely to change Iranian thinking once again go up the agenda.

The impasse will cast a shadow over Trump’s summit with the Chinese president Xi, Jinping, which starts in Beijing on Thursday. China has deep economic ties to Iran, and Xi is unlikely to agree to any request from Trump to restrict oil purchases or arms sales between Beijing and Tehran.

There has been expectations that the US president would like the Iran war off the agenda by the time he sat down for his most important summit of the year. Despite postponing the visit in late March, Trump appears nowhere close to an agreement withTehran. He is left re-examining military options to try to recover Iran’s stockpile of highly enriched uranium, but Iranian officials said the stockpile was protected.

The standoff means that individual shipping companies are still negotiating with either Iran or the US to bypass the blockades in the strait of Hormuz, but the overall number of tankers being allowed through remains minuscule. The greatest tension on Monday focused on a cargo of Emirati liquefied petroleum gas that was sailing under the Panamanian flag and departed from the port of Sharjah.

Badr bin Hamad Al Busaidi, Oman’s foreign minister, the state on the south side of the strait, held talks with Arsenio Dominguez, the secretary general of the International Maritime Organization, a UN agency, to try to reach agreement on a new regime for the important waterway, as well as urgent humanitarian measures to help crews who have been stuck on oil tankers for weeks.

Almost 1,500 tankers and 20,000 seafarers are stranded in the Gulf, the IMO estimates. Dominguez said supplies – including water, food and fuel – would soon start running short.

The Iranian plan dismissed by Trump largely focused on ending the US blockade in the strait, but leaving the issues surrounding Iran’s nuclear programme to a negotiation starting after 30 days of confidence building, a deferral that the US president and Israel reject. Tehran argues the previous use of US bases in the region to attack Iran means the “strait can no longer be treated as a normal and neutral waterway”.

There are also signs that pressure continues to mount on the Iranian economy. Tehran city council said offices had been ordered to reduce electricity consumption by 30% during office hours and by 70% in non-office hours. The ruling applies to public and private offices. The head of the national society of internal medicine specialists said there was a serious decrease in the country’s medicine reserves.

Estimates show the direct daily cost from Iran’s internet shutdowns is about $30m to $40m in lost sales, with the indirect damage about double that.

The Iranian parliament has not been meeting in public during the war, but has started to hold online sessions as advised by the country’s supreme national security council.

The Iranian reformist press said: “Inflation, reduced purchasing power and concerns about the supply of essential goods has put heavy pressure on public opinion.”

On Tuesday, the UK and France will hold a meeting of as many as 40 defence ministers to discuss the contributions to a taskforce to protect free naval passage in the strait of Hormuz after any US-Iran agreement.