Iran hit out Thursday at the United States for sticking to what it called former president Donald Trump's "failed policy", saying such an approach would fail to salvage a nuclear deal.

"US claims it favours diplomacy; not Trump's failed policy of 'maximum pressure'," Iran's Foreign Minister Mohammad Javad Zarif wrote on Twitter.

"Yet (US Secretary of State Antony Blinken) boasts abt blocking Korea from transferring our OWN money to the Swiss Channel -- only used for food & meds," he added.

"Repeating the same policy won't yield new results."

Zarif's comments came hours after Blinken signalled US opposition to the release of billions of dollars in Iranian funds from South Korea unless the Islamic republic returns to full compliance with the nuclear accord.

South Korea had said last month it agreed on a way forward to release billion of dollars frozen from Iran's oil sales but was awaiting Washington's approval.

US President Joe Biden, who defeated Trump at the ballot box in November, has signalled his readiness to revive the deal that has been largely left in tatters by his predecessor's decision to withdraw from it in 2018.

But Biden insists Iran first return to its nuclear commitments, most of which it suspended in response to US sanctions, while Tehran demands Washington take the first step by scrapping them.

Iran was a key oil supplier to resource-poor South Korea until Washington's rules blocked the purchases.

According to government spokesman Ali Rabiei, Iran has $7 billion of funds blocked in Seoul.

Iran's Revolutionary Guards on January 4 seized a South Korean tanker and arrested its multinational crew near the strategic Strait of Hormuz, saying it had polluted the waters.

Tehran has on various occasions denied the seizure and the funds are linked.