Iran's Atomic Energy Organization (IAEA) chief Ali Akbar Salehi on Monday warned the signatories of the nuclear deal in 2015 of "serious consequences" unless they act to preserve the economic benefits of the deal.

Speaking to reporters on the sidelines of a seminar in Brussels on nuclear cooperation, Salehi said he hoped the political situation expressed by the EU, China and Russia would become actionable.

"If the words do not turn into actions, it will have dire consequences that are unpredictable. If the agreement collapses, the situation will change and everything will be in turmoil."

The EU hosted Salehi at a seminar on nuclear cooperation aimed at showing the bloc's continued support for the nuclear deal after the re-imposition of US sanctions targeting Iran's oil exports this month.

The EU and other signatory parties hope to persuade Tehran to observe the restrictions imposed by the agreement on its nuclear program despite Washington's withdrawal, which deprives Iran of many economic benefits.

European Union efforts to salvage trade relations with Tehran, including a special non-dollar transaction mechanism, are stalled.

"There should be no doubt about the level of political ambition and determination of the countries concerned, particularly France, Germany and the United Kingdom, to activate a targeted mechanism quickly," European Climate and Energy Commissioner Miguel Arias Canetti told a joint press briefing.

The target mechanism, such as a clearinghouse that could be used to swap Iran's oil and gas exports with commodity sales from the European Union, would be in a swap deal in practice. But none of the EU countries has offered to host the mechanism, delaying the plans.