Iran’s foreign minister has warned the US that failure to agree a nuclear deal was likely to herald the political demise of pragmatist president Hassan Rouhani, Iranian officials said, raising the stakes as the decade-old stand-off nears its endgame.

Mohammad Javad Zarif pressed the concern with the US secretary of state, John Kerry, at several meetings in recent weeks, according to three senior Iranian officials, who said Iran had also raised the issue with other western powers.

Western officials acknowledged the move might just be a negotiating tactic to persuade them to give more ground, but said they shared the view that Rouhani’s political clout would be heavily damaged by the failure of talks.

The warning that a breakdown in talks would empower Iran’s conservative hardliners comes as the 12-year-old stand-off reaches a crucial phase, with a March deadline to reach a political agreement ahead of a final deal by 30 June.

The agreement aims to end sanctions in exchange for curbs on Tehran’s nuclear programme, though hard-to-bridge differences remain, particularly on the timing of the relief on economic sanctions and the duration of the deal.

Both Barack Obama and Rouhani, who Iranian officials say has staked his career on the deal, are facing stiff domestic opposition to an agreement, narrowing the scope for compromise.

A senior US official denied that any such warnings had been received from the Iranians. “We’ll leave assessment of Iranian politics to the Iranians but this rumor is untrue,” the official told Reuters on condition of anonymity.

But the Iranian officials insisted that Zarif had raised the concern with Kerry. The two have met repeatedly in recent weeks in an attempt to break the impasse, most recently on Friday when they talked for over an hour on the sidelines of the Munich Security Conference.

“As Rouhani is on the frontline, naturally he will be more harmed,” said one of the officials, who has direct knowledge of Zarif’s discussions with Kerry.

Other western officials said the Iranian delegation had raised the same concern in talks recently. If the talks fail, Rouhani would likely be sidelined and his influence dramatically reduced, giving hardliners such as Iran’s Revolutionary Guard Corps an upper hand, Iranian officials and western analysts say.

A comprehensive nuclear deal is seen as crucial to reducing the risk of a wider Middle East war, at a time when Iran is deeply involved in conflicts in Syria and Iraq. After nearly a year of talks, negotiators failed for the second time in November to meet a self-imposed deadline for an agreement.

The key sticking point in the talks at the moment is Iran’s demand that western powers agree to the quick end of oil and banking sanctions, western and Iranian officials say.

One of the Iranian officials, who also had direct access to the talks, said the Americans were talking in terms of years for the sanctions relief while Iran wanted curbs on oil and banking to be lifted within six months.

Rouhani was elected in 2013 on promises of ending the crippling western sanctions, improving the economy and reducing the country’s diplomatic isolation.

But he faces a worsening power struggle with Iran’s supreme leader, Ayatollah Ali Khamenei, who has said Iran should immunise itself against sanctions, suggesting that he is prepared to live with them. Khamenei has the final word on any deal.