Qatar has stepped up its role in mediating between the US and Iran as western powers have been striving to convince wary Iranian leaders to ink a deal to revive the 2015 nuclear accord, according to people briefed on the talks.

After 11 months of EU-brokered indirect talks in Vienna, officials say time is running out. The Gulf state has been acting as an intermediary at the request of both Washington and Tehran, complementing the talks in the Austrian capital, in an effort to build trust between the longtime foes.

Doha has ferried messages between the protagonists and sought to allay Iranian concerns, including those related to its demand that the Biden administration provide a guarantee that no future US government is able to unilaterally abandon the deal, as former president Donald Trump did in 2018.