TEHRAN: Iran on Thursday accused the United States of working to “complicate” efforts to restore a 2015 nuclear deal, after new Russian demands linked to its invasion of Ukraine raised concerns of further delays.

It came on the day Iran’s supreme leader Ayatollah Ali Khamenei, who has the final say in major state policies, stressed that his country will not give up on elements of “national strength”, such as nuclear progress and regional influence.

Tehran is locked in negotiations with world powers to revive the nuclear deal that offered it sanctions relief in return for curbs on its atomic programme.

Its arch foe the United States, under former president Donald Trump, unilaterally withdrew in 2018 from the accord known formally as the Joint Comprehensive Plan of Action.

Moscow said on Saturday that, before backing a revived deal, it wants written assurances from Washington that sanctions imposed on it over the Ukraine war will not affect its economic and military cooperation with Tehran.

“Vienna negotiations are becoming more complicated every hour without a political decision by the United States,” Iran’s top security official Ali Shamkhani tweeted on Thursday.

“US approach to Iran’s principled demands, coupled with its unreasonable offers and unjustified pressure to hastily reach an agreement, show that US isn’t interested in a strong deal that would satisfy both parties,” he added.

The negotiations to revive the deal involve Iran as well as France, Germany, Britain, Russia and China directly, and the United States indirectly.

Washington’s unilateral withdrawal from the accord and its re-imposition of biting economic sanctions prompted Iran to begin rolling back on its own commitments.

Negotiators have signalled that talks had progressed into a “final phase”, but pending issues were still unresolved.

The United States has described Russia’s new demands “irrelevant”, while France warned they could dash hopes for a revived nuclear accord.

“Some people are trying to blame us for protracting the talks. I must tell you that the talks have not yet been finalised, even the text of final agreement is not yet finalised,” Russian chief negotiator Mikhayil Ulyanov said on Wednesday.

“Like any other participant we have the right to ask for something... It’s normal business, those who don’t understand it are not professionals,” he added.

“We have the right to protect our interest both in the nuclear field, as well as in the wider context,” he said, adding that he believes “all our trade and economic relations with Iran should be exempt from current and future EU or US sanctions”.’

The July 2015 deal gave Iran sanctions relief in exchange for curbs on its nuclear activities to guarantee it could not develop a weapons capability — an ambition it has staunchly denied.

Western countries have also voiced concern over other Iranian capabilities, including its ballistic missiles program and regional influence and ties to armed groups from Lebanon to Yemen.

Iran’s supreme leader said on Thursday that matters of “national strength” were not up for negotiation. “Regional presence gives us strategic depth and more national strength. Why should we give it up?” Khamenei said, in a statement on his official website.

“Nuclear scientific progress is also related to meeting the needs of the country in the near future, and if we give it up, from who and where we should ask for that in a few years?”

Reducing defensive capabilities in compliance with what the “enemy” wants is “naive and amateurish”, he added.