Iran's Foreign Minister Hossein Amir Abdollahian said on Tuesday that the ball is now in the U.S.'s court to ensure a successful conclusion of the Vienna talks on restoring the 2015 Iran nuclear deal. 
  
"If Washington responds to the few remaining important issues and does not waste time anymore, Vienna talks can be concluded soon," Amir Abdollahian said when meeting his Russian counterpart Sergei Lavrov in Moscow, according to the website of the Iranian Foreign Ministry. He described Russia's approach to the Vienna talks over the past 11 months as "constructive," expressing confidence that this approach would continue until a good and credible agreement is reached. 

For his part, Lavrov reiterated Russia's full support for the conclusion of the talks, stressing that the country would not stand in the way of a Vienna agreement.

Under the Iran nuclear deal, formally known as the Joint Comprehensive Plan of Action (JCPOA), Iran accepted some restrictions on the development of its nuclear program in return for removal of UN and Western sanctions. However, then U.S. President Donald Trump withdrew the country from the deal unilaterally in 2018, and reinstated old and new sanctions against Iran. Tehran retaliated by dropping some of its nuclear commitments.

Since April 2021, eight rounds of negotiations have been held between Iran and the remaining parties to the JCPOA, with the United States indirectly involved, aimed at removal of sanctions against Iran and the restoration of the pact. 

But the talks, which are nearing an agreement, were halted last week, after Russia reportedly demanded guarantees that the U.S.-led sanctions imposed over the Ukraine crisis should not affect its trade ties with Iran. 
  
Lavrov said on Tuesday that Russia has written guarantees it can carry out its work as a party to the Iran nuclear deal. 

"We have received written guarantees – they are included in the very text of the agreement on reviving the JCPOA, and in these texts there is a reliable defense of all the projects provided for by the JCPOA and those activities – including the linking up of our companies and specialists," the Russian foreign minister said at a joint press conference with his Iranian counterpart. 

U.S. State Department spokesperson Ned Price said on Tuesday that the United States will not sanction Russian participation in nuclear projects in Iran under a revived nuclear deal, but would not allow Russia to use the deal as an "escape hatch" to evade Ukraine-related sanctions. 

Mikhail Ulyanov, Russia's envoy to the Vienna talks, said last week that the conclusion of the negotiations was not solely dependent on Moscow. 

"The conclusion of the deal does not depend on Russia only," Ulyanov told reporters. "There are others actors who need additional time and who have additional concerns and they are being discussed." 

China has stressed that the concerns and demands of all parties to the Vienna talks must be addressed properly. 

(With input from Xinhua, Reuters)