In an interview with IRIB, Saeed Khatibzadeh reacted to the reports that the British officials have acknowledged efforts to pay a debt to the Iranian government, deploring attempts to link such acknowledgment to a possible release of British dual national Nazanin Zaghari-Ratcliffe, who is serving prison term in Iran after being convicted of espionage.

He said the UK government is definitely in debt to Iran for the non-delivery of Chieftain tanks ordered more than 40 years ago “no matter whether a UK government official acknowledges the debt or not.”

Ms. Zaghari has served part of her sentence in Iran and has been even released on parole, the spokesman said, noting that her case has gone through ordinary judicial procedures and is not any different from other inmates.

His comments came after UK Defense Secretary Ben Wallace for the first time acknowledged that he is actively seeking to pay a debt to the Iranian government that may finally help to secure the release of Zaghari-Ratcliffe.

The UK is thought to owe as much as £400m to the Iranian government arising from the non-delivery of Chieftain tanks ordered by the former regime of Iran before the 1979 Islamic Revolution.

An international arbitration in 2008 ruled the UK owed the debt, but in subsequent protracted court battles, lawyers acting for International Military Services, the UK Ministry of Defense’s now-defunct arms sales agency, have questioned not only the debt’s size, but at times whether any debt was payable.

The admission came in a letter to the lawyers acting for British-Iranian national Nazanin Zaghari-Ratcliffe, who is serving a five-year sentence in Iran for espionage.

Wallace said UK is seeking ways to pay off the defense debt to Iran, which is estimated to be as much as £400 million arising from the non-delivery of tanks ordered by Iran’s ousted monarch Mohammad Reza Pahlavi, The Guardian reported.

International Military Services (IMS), a subsidiary of the British Ministry of Defense, signed contracts in 1971 to sell more than 1,750 Chieftain tanks and armored vehicles to Iran. The deals were cancelled after the Shah was deposed in the 1979 Islamic Revolution, but Iran had already paid for the undelivered tanks and demanded its money back.

An international arbitration in 2008 ruled the UK owed the debt, but it has not yet paid up.

“With regard to IMS Ltd and the outstanding legal dispute the government acknowledges there is a debt to be paid and continues to explore every legal avenue for the lawful discharge of that debt,” Wallace wrote.

“I have previously stated my personal position and I remain committed to its resolution, but it would not be appropriate for me to comment further at this time,” he added.

Before becoming defense secretary, Wallace had been sharply critical of the British government’s delay in settling its debt, describing it as “un-British, double-dealing and obfuscatory”.

Britain has repeatedly refrained from paying the debt, citing illegal sanctions imposed by the United States on Iran.