Iran's hardline President Ebrahim Raisi said on Monday that the US should lift sanctions, as Tehran has refused to return to nuclear talks since in June.

"We are serious about result-oriented negotiations. ... If Americans are serious, they should remove unjust sanctions on Iran," Raisi told state TV.

In April, Iran and six powers started talks to reinstate the deal that then-US President Donald Trump ditched three years ago and reimposed sanctions that have squeezed Iran's oil exports.

The talks in Vienna were meant to agree on a process for both sides to return to the 2015 agreement (JCPOA), which would involve lifting of US sanctions, and for Iran stopping violations of the deal.

But the talks were put on hold after Raisi's election in June. Western powers have urged Iran to return to negotiations, warning that time is running out as Tehran's nuclear program is advancing well beyond limits of the nuclear pact.

In response to Trump's reimposition of sanctions, Tehran has breached the deal by rebuilding stockpiles of enriched uranium, refining it to higher fissile purity and installing advanced centrifuges to speed up output.