The Advisor to the Iranian nuclear negotiation team has stressed that the situation of the western countries does not let them put more pressure on Iran.

The initial nuclear deal signed in 2015 by Iran, the US, UK, France, and Germany – as well as Russia, China, and the EU – involved Tehran agreeing to certain restrictions on its nuclear industry in exchange for easing economic sanctions and other incentives.
Mohammad Marandi said on Sunday that Iran needed guarantees before the signing of the new agreement. 
He said that the Americans and Europeans are in tough conditions, so they were unable to put more pressure on Iran."
"Gas was of paramount importance now, and the Americans and Europeans knew it", he stated.
Efforts to revive the 2015 nuclear talks, despite notable progress, by US indecisiveness and procrastination have led to multiple interruptions so far.

In 2018, the US unilaterally withdrew from the JCPOA, reimposing sanctions on Iran under a 'Maximum Pressure' campaign.