Iran’s supreme leader has suggested that the United States created “a special version” of the deadly coronavirus now ravaging the country.

The disease has killed at least 1,685 Iranians, including 129 in the last 24 hours.

Ayatollah Ali Khamenei, Iran’s top political, military and religious leader, spurned offers of US help in a speech on Sunday marking the beginning of the Persian calendar year. He suggested Washington would exploit any acceptance of American aid.

“The American leaders have said several times that ‘we are willing to provide you with treatment and medical assistance’,” he said. “First of all, you face shortages yourselves. If you have anything available, use it yourselves. Second, you, Americans, are accused of producing this virus. I do not know how true this accusation is. But as long as this accusation stands, which sane mind will trust you?”

Iran has a history of attempting to deflect its own failings onto western powers, especially the US and the UK.

On Saturday, Iran’s deputy health minister accused the UK of impeding its efforts to halt the spread of coronavirus by preventing the sale of 1 million surgical masks because of United States sanctions.

“We had bought several million masks from Britain before [the epidemic started] but the country did not deliver them to us due to the sanctions,” Alireza Raisi told the hardline Fars News Agency.

He did not provide any evidence or details of the purportedly scuttled deal, nor specify whether it was through a private firm that may have decided on its own not to follow through with the deal.

If substantiated, the case would amount to the most concrete example of how US sanctions imposed on countries and companies that do business with Iran are impeding efforts to halt coronavirus in one of the worst-hit countries, surpassed so far only by contagions in Italy and China.

A Foreign Office spokesperson referred The Independent to a 2 March statement of solidarity with Iran, in which the UK, France and Germany commit €5 million to help Iran fight the pandemic.

More than 21,000 people have tested positive for coronavirus in Iran. Mr Khamenei said the US could use aid offers as a way “to further spread this disease” to disrupt Iran. Washington and Tehran are in the midst of a standoff sparked by the White House’s withdrawal from the 2015 nuclear deal.

In conspiratorial remarks, Mr Khamenei suggested the US brewed a special version of the virus “based on Iranian genetic information they have gathered”.

He provided no evidence for his statement. Covid-19 has struck the US hard, killing at least 388 people so far as it hammers and overwhelms urban and rural health systems.

Iran says it has been hampered by US sanctions, which Washington tightened after confrontations between American-backed forces and Iranian-backed militias in Iraq this month.

Mr Raisi said that numerous medical staff had come down with Covid-19 because of shortages of protective equipment and masks, and that efforts to obtain the materials in the world market had been complicated by US sanctions. The US rules were imposed after Donald Trump’s administration withdrew the nuclear deal and launched an aggressive attempt to economically besiege the country.

“We are facing serious problems for ordering, purchasing and transferring money due to the sanctions,” Mr Raisi told the news agency. “We cannot buy ventilator systems and ICU [intensive care unit] beds. Also, transferring money to purchase certain drugs is not possible for us.”

Like Iran, the US, UK and other countries are facing shortages of surgical masks as the coronavirus spreads throughout the world, with horror stories of doctors forced to reuse medical supplies for days emerging from numerous hospitals.