Iran's Supreme Leader Ayatollah Ali Khamenei accused U.S. President Joe Biden and his predecessor Donald Trump of damaging the reputation of the United States in a rare direct criticism of U.S. presidents, Iran's official news agency IRNA reported on Tuesday. 

"These days, the U.S. is being hit in ways it never computed. The two American presidents – the current and former heads of state – have joined hands to tarnish the image of the United States," Khamenei said without elaborating. 

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Crunch time for the JCPOA

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Iran and the United States resumed indirect talks in Vienna on Tuesday to revive a 2015 nuclear deal that Trump left in 2018.

While the U.S. State Department says such negotiations are entering their "final stretch," Iranian officials have declared that part of their demands on sanctions removal have so far been left unaddressed in the Vienna talks. 

"A deal that addresses all sides' core concerns is in sight, but if it is not reached in the coming weeks, Iran's ongoing nuclear advances will make it impossible for us to return to the JCPOA," a U.S. State Department spokesperson said on Monday, referring to the official name of the deal (Joint Comprehensive Plan of Action). 

Both sides say that they await a final political decision from the other to revive the nuclear deal.  

On Tuesday, Iran's top security official, Ali Shamkhani, warned on Twitter that "the path to negotiations will not be smooth" should the current U.S. administration continue with the maximum pressure campaign launched against Iran by Trump. 

"Continuing maximum pressure against #Iran, current U.S. administration has so far tried to meet the goals that Trump failed to achieve through bullying, by making unsupported promises," Shamkhani tweeted.   

Under the nuclear agreement reached in June 2015, Iran accepted some restrictions on the development of its nuclear program in return for removal of the UN and Western sanctions. However, the Trump administration withdrew from the deal unilaterally in 2018, and reinstated old and new sanctions against Iran. Tehran retaliated by dropping some of its nuke commitments. 
  
Since April 2021, several rounds of negotiations have been held between Iran and the remaining parties to the deal, with the United States indirectly involved, aimed at removal of sanctions against Iran and the restoration of the deal. 

(With input from agencies)