The minister’s remark comes in response to a US State Department demand for Tehran to release several American citizens before the start of swap negotiations.

Iranian Foreign Minister Mohammad Javad Zarif said it is the US that must prove that its intentions are serious when it comes to prisoner exchange, as Iran has already done so by adhering to the Iranian Nuclear deal.

"We're not supposed to show seriousness because we have shown our seriousness by implementing the nuclear deal", Zarif said in an interview with CBS.

He underscored that Tehran is not linking the two issues, but rather using the Nuclear Deal as an example of Iran's reliability.

"We've shown that when we say something, we abide by it", he said. "The United States has shown that when they say something, they will then decide whether they want to abide by it or not".

"We're not linking the two [issues]", he added.

His comments come in response to a demand by a US State Department spokesperson who in a statement on Saturday suggested that Iran could show seriousness by releasing "innocent US persons", according to The Hill.

"The Iranian regime can demonstrate its seriousness regarding consular issues, involving Iranians who have been indicted or convicted of criminal violations of US sanctions laws, by releasing innocent U.S. persons immediately", the spokesperson said.

"We call on Iran to free all unjustly detained and missing U.S. persons, including Xiyue Wang, Robert Levinson, Siamak Namazi, and Nizar Zakka, among others", the spokesperson added.

Wang, Namazi, and Zakka have been detained in Iran on espionage allegations. Robert Levinson was a CIA agent sent to Iran on an unauthorised spy mission, according to a report by The New York Times. When Levinson's mission became known to US top brass, three agency officials reportedly lost their jobs for "using Mr. Levinson as part of an unauthorized spying operation".

On 24 April, Zarif offered the US an exchange of all prisoners.

"I put this offer on the table publicly now: Exchange them", he said at the Asia Society in New York. "I am ready to do it and I have the authority to do it".

Earlier this week, Zarif said he thinks that while US President Trump does not want an open conflict with Iran, he is seeking to bring Tehran to its knees by applying economic sanctions and political pressure.

"Iranians are allergic to pressure", he said.

After US President Donald Trump unilaterally withdrew from the so-called Iranian Nuclear Deal in 2018, the International Atomic Energy Agency (IAEA) confirmed that Tehran was in compliance with its commitments under the deal.

"Iran is subject to the world's most robust nuclear verification regime under the JCPOA, which is a significant verification gain. As of today, the IAEA can confirm that the nuclear-related commitments are being implemented by Iran", IAEA Director General Yukiya Amano said in May of last year.