The governor of Tehran's central bank on Tuesday said that Iran might well use the frozen funds released to it under its deal with Washington to buy US farm products.

But Abdolnaser Hemmati, in a video message, denied US President Donald Trump's declaration that the agreement obliges Iran to spend the money on American exports.

Hemmati said it was true that the initial $12 billion released to Tehran was to be used to buy 'essential goods and medicine', adding that this would free Iran to spend its regular funds on whatever it wants.

Trump said Tuesday that Iran's money would be 'used for the purchase of food and medical supplies, exclusively from the United States, including Corn, Wheat, and Soybeans from our great American Farmers.'

But Hemmati reassured his fellow Iranians: 'That is not true. There is no such requirement in the memoranda that were signed during the negotiations. There is no obligation to buy from the United States.

'However, we also see no problem with purchasing from the United States if the price and quality of essential goods -- whether corn, wheat, or any other products we need -- are competitive,' he said.

Hemmati also clarified Iran's understanding of the agreement's provisions to end the sanctions banning Iran's exports of oil and petrochemicals.

During the 60-day negotiating period, he said, Iran would be free to export petroleum products 'free from sanctions-related pressures', including financial restrictions.

'We would be able to deliver these products through any port, using any vessel, and receive payment into whatever accounts we designate ... so that we could freely use the proceeds,' he said.

Trump has faced criticism for signing a deal with Tehran to halt the US-Iran war and to begin releasing billions of dollars in frozen Iranian assets, before any agreement on the future of its nuclear programme.

But on Tuesday he posted on social media that the frozen funds would go into a US-controlled escrow account and used to buy vital food and medicines -- not to fund, for example, Iranian re-armament.

Hemmati nonetheless played down these restrictions.

'For us, it makes little difference. Every year we spend roughly $10 to $12 billion, and perhaps even closer to $15 billion, on essential goods,' the central banker explained.

'If these released funds are used for those imports, then the resources we would otherwise have allocated ourselves can instead be used elsewhere or saved as reserves.'