Iran's top security official says the fate of the Vienna nuclear negotiations is tied to delays in the political decisions by the United States.

The secretary of Iran’s Supreme National Security Council, Ali Shamkhani, repeated an Iranian argument on Monday that the “prospect of a deal in Vienna talks remains unclear due to Washington's delay in making political decisions”.

The priority of Iranian negotiators is to resolve the remaining issues that are considered as the red lines for Tehran, he added, calling for “new initiatives from all parties” for a swift conclusion to a “strong deal.”

In another tweet earlier in the day, Shamkhani said, "Vienna participants act and react based on [their own] interests and it's understandable. Our interactions with 4+1 are also solely driven by our people's interests. Thus, we're assessing new elements that bear on the negotiations and will accordingly seek creative ways to expedite a solution”.

Iran’s foreign ministry said Monday that Tehran is awaiting clarification from Moscow over its demand to be exempted from Ukraine sanctions in its dealing with Iran.

"We have seen and heard about [Russian Foreign Minister Sergei] Lavrov's comments in the media. We are awaiting to hear its details through diplomatic channels," the ministry’s spokesman Saeed Khatibzadeh said at his weekly press conference.