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 on 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.

"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 the United States and its allies.