The revival of the 2015 Iran nuclear deal is looking bleak after last-minute Russian demands and disagreements between the United States and Iran winded back negotiations. Preparations were being made last week for a weekend meeting in Vienna that would have concluded with a potential agreement that would bring back Iran’s compliance to the non-proliferation of nuclear weapons and the US into the agreement after their exit in 2018.

Negotiations took a turn last March 6 after sweeping demands from Moscow via Russian Foreign Minister Sergei Lavrov asked for a US guarantee that Russian-Iran trade will be protected from sanctions brought by the invasion of Ukraine. Initially, the Russian demands upset Iran and made it seem that the move pushed Tehran and Washington to iron out the remaining issues on the agreement. However, a sudden barrage of remarks from Iranian officials, which included Supreme Leader of Iran Ali Khamenei on March 10, suggested a change of heart.

“US approach to Iran’s principled demands, coupled with its unreasonable offers and unjustified pressure to hastily reach an agreement, show that US isn’t interested in a strong deal that would satisfy both parties,” said Iranian top security official Ali Shamkhani in a tweet.

“Absent US political decision, the talks get knottier by the hour,” said Shamkhani, who did not provide further detail on the demands in question.

The United States has reiterated on March 10 that it will not entertain Moscow’s last-minute demands, which, according to them, “have nothing to do with the deal with Iran.”