Indirect talks between Washington and Tehran on reinstating their nuclear pact broke off on Friday, with both sides saying they would resume the following week, as Western officials voiced dismay at sweeping demands by the Islamic Republic.

"It is now clear that Washington's reluctance to give up sanctions altogether is the main challenge to the progress of the talks," the unnamed official was quoted as saying by Iran's Tasnim news agency.

"We believe that a deal is within reach if the US government gives up its campaign of maximum pressure and the European parties show serious flexibility and political will in the talks."

Iran and major powers started talks in April aimed at bringing back Tehran and Washington into full compliance with the pact, which was abandoned by former US President Donald Trump three years ago.

But the talks stopped after the election of Iran's hardline President Ebrahim Raisi in June.

A year after Trump's reimposition of harsh sanctions on Iran, Tehran began to gradually violate nuclear limits of the agreement.

Iran wants all sanctions imposed by the United States to be lifted in a verifiable process.

While stressing that the United States still wanted to revive the deal, under which Iran had limited its nuclear program in return for relief from economic sanctions, a senior US State Department official said on Saturday time was running short.

Australian Associated Press