Iran’s Foreign Minister Mohammad Javad Zarif says the US has a “legal and moral obligation” to remove sanctions on Tehran, turning the tables on Washington after Secretary of State Antony Blinken demanded that the Islamic Republic “come back into compliance on the nuclear side”.

“Lifting Trump’s sanctions, Secretary Blinken, is a legal and moral obligation. Not negotiating leverage,” Zarif tweeted Monday in a post addressed to the top US diplomat.

The administration of President Joe Biden is showing an aversion to remove a web of sanctions which its predecessor imposed on Iran with the aim of negotiating what it characterized as a better nuclear deal with the Islamic Republic.

Washington’s resistance has complicated the negotiations currently underway in Vienna to bring the US back to compliance with the nuclear deal, officially known as the Joint Comprehensive Plan of Action (JCPOA), which former president Donald Trump abandoned in 2018.

While the US is not a party to the negotiations, it has sent a delegation to the Austrian capital in order to make its presence felt as much as possible.

On Sunday, Blinken sought to put the ball in Iran’s court, saying the United States had not seen yet whether Iran would move to comply with its nuclear commitments in order to have the sanctions removed.

“Iran, I think, knows what it needs to do to come back into compliance on the nuclear side, and what we haven’t yet seen is whether Iran is ready and willing to make a decision to do what it has to do. That’s the test and we don’t yet have an answer,” Blinken told ABC News.

In his Monday posts, Zarif dismissed Blinken’s political grandstanding, saying it “didn’t work for Trump—won’t work for you”.

“Release the Iranian people’s billions of dollars held hostage abroad due to US bullying,” he said.

“Trump’s legacy is past its expiration date. Drop it, president of the United States.”

With a fifth round of talks in coming days, Blinken’s comments poured fresh cold water on the prospects of a breakthrough in the standoff.

Iran is adamant that the US make the first move to undo its wrongs and lift all its sanctions in one go because it was the side which reneged on its commitments and abandoned the JCPOA.

After a year of fruitless waiting for the remaining signatories to support Iran and protect it from the sanctions, the Islamic Republic finally took a series of “remedial” measures under an article of the JCPOA, which have seen the country let go of some of the restrictions on its nuclear activities.

With the negotiations dragging on, patience is running out in Iran where the government is obliged to implement the Strategic Action Plan to Counter Sanctions passed by the parliament in December to step up the remedial measures.

Iran’s top nuclear negotiator Abbas Araqchi on Monday tweeted that he spent four hours before the parliament’s Foreign Policy and National Security Commission to brief the MPs on the Vienna talks.

“Very tough. But useful,” he wrote of the meeting. The bottom line is, he said, “having left the JCPOA, the US must first provide verifiable sanctions lifting. Iran will then resume full implementation”.