In this May 24, 2021 file photo, the flag of Iran waves in front of the International Center building with the headquarters of the International Atomic Energy Agency, IAEA, in Vienna, Austria. (FLORIAN SCHROETTER / AP)

DUBAI - The United States is responsible for the pause in talks between Tehran and world powers in Vienna aimed at reviving their 2015 nuclear deal, an Iranian foreign ministry spokesperson said on Monday.

"America is responsible for the halt of these talks ... a deal is very much within reach," Saeed Khatibzadeh told a weekly news conference.

The US State Department said on Thursday that a small number of outstanding issues remain in the nuclear talks, adding that the onus was on Tehran to make those decisions

"Washington should make political decision for the deal's revival," he said, adding that Tehran would "not wait forever".

The US State Department said on Thursday that a small number of outstanding issues remain in the nuclear talks, adding that the onus was on Tehran to make those decisions.

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Iran has said that there are still outstanding issues, including Washington removing a foreign terrorist organization (FTO) designation against Iran's Islamic Revolutionary Guard Corps (IRGC).

Also Tehran has been pushing for guarantees that any future US president would not withdraw from the agreement. The extent to which sanctions would be rolled back is another unresolved issue.

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Khatibzadeh also said Tehran was ready to resume talks with its key regional rival, Saudi Arabia, if Riyadh showed willingness to resolve outstanding bilateral issues.