Vienna, Austria - Negotiations on reviving the 2015 Iran nuclear deal are set to resume on Monday in Vienna amid few signs of progress and a tense atmosphere.

Five months after the last round of talks, high-ranking diplomats from Germany, France, Britain, Russia, and China are returning to the Austrian capital to mediate between representatives of Tehran and Washington.

"We don't think the West wants an agreement," Iranian chief negotiator Ali Bagheri said on the eve of the talks.

His US counterpart, Robert Malley, recently indicated a shift towards a tougher stance if Tehran does not relent.

Melania Trump Melania Trump makes big comeback at closed-door LGBTQ+ fundraiser

A quick breakthrough is not expected.

The goal of the talks is to salvage the landmark 2015 agreement, which restricted Iran's nuclear program in an effort to prevent the country from developing nuclear weapons. Western sanctions were lifted in return.

But the US torpedoed the pact in 2018, when it pulled out unilaterally under Donald Trump and revived sanctions that severely hit Iran's economy. President Joe Biden hasn't shown any interest in reversing his predecessor's move so far and has kept up the confrontational tone.

Tehran has since once again expanded its nuclear facilities, producing near-weapons-grade uranium and limiting international inspections.

Now both sides are seeking ways to de-escalate the rift.