Iran will stay in the Vienna nuclear talks until its demands are met and a "strong agreement" is reached, Iran's top security official Ali Shamkhani said Monday.

Talks to revive the 2015 Iran nuclear pact face the prospect of collapse after a last-minute Russian demand forced world powers to pause negotiations for an undetermined time despite having a largely completed text.

Russian foreign minister Sergei Lavrov demanded on March 5 that his country’s economic and other ties with Iran to be exempted from Western sanction related to the invasion of Ukraine. The United States and its European allies have rejected the demand.

Iran, which blames the United States and NATO for the Ukraine invasion, has not criticized Moscow’s last-minute demand.

"We will remain in the Vienna talks until our legal and logical demands are met and a strong agreement is reached," Shamkhani, secretary of the Supreme National Security Council, which makes the decisions in the Vienna talks, said in a tweet.

Tensions have risen since Iran attacked Iraq's northern city of Erbil on Sunday with a dozen ballistic missiles in an unprecedented assault on the capital of the autonomous Iraqi Kurdish region that appeared to target a new building for the US consulate in the city.