Iran said Thursday it hopes the UN nuclear watchdog will act "neutrally" under its new head and vowed to maintain cooperation with its inspectors monitoring a landmark 2015 nuclear deal.

Argentina's Rafael Grossi took the helm of the International Atomic Energy Agency on Tuesday following the death of his predecessor, Yukiya Amano of Japan, in July.

The UN agency is tasked with monitoring Tehran's nuclear activities to assess its compliance with the 2015 agreement with major powers, which has been severely undermined by Washington's abandonment of it in May last year.

Iran hopes that during Grossi's tenure, the IAEA "can neutrally and professionally undertake its international responsibilities and sensitive missions," foreign ministry spokesman Abbas Mousavi said in a statement.

"Iran is ready to maintain and expand interaction and cooperation with the agency with goodwill and mutual respect," he added.

Tensions with the United States have escalated sharply since it began reimposing crippling unilateral sanctions lifted under the nuclear deal.

The European parties to the deal -- Britain, France and Germany -- have repeatedly said they are committed to saving the accord, but their efforts have so far borne little fruit.

Tehran has hit back by suspending its compliance with parts of the deal until sanctions relief is restored.

"The path for diplomacy is open... the Europeans and especially the French are still trying to act on their commitments," Mousavi told state television.

Yet the attempts have so far "failed to reach any tangible results" and "if the situation goes on as it is, (Iran) will most probably take the fourth step," he added.

Iran has said it will unveil a fourth package of measures on Monday.