Iran said it will attend a meeting in Vienna on Sunday of diplomats from countries still party to the 2015 nuclear deal, as they try to salvage the landmark agreement.

The hard-won deal has been threatened with collapse since the United States withdrew from it last year and reimposed biting sanctions against Iran as part of a "maximum pressure" campaign.

"It was agreed to convene an extraordinary meeting of the JCPOA joint commission in Vienna on July 28," Iran's Foreign Ministry said on Tuesday, using the acronym for the deal's formal name, the Joint Comprehensive Plan of Action.

The meeting would be held at the level of deputy ministers and political directors, it said in an English-language statement.

It was requested by the European parties to discuss the "new situation", the statement added, referring to Iran's reduced nuclear commitments under the deal in response to the U.S. withdrawal.

Iran said on May 8 it would disregard certain limits of the deal as long as the remaining parties – Britain, China, France, Germany and Russia – fail to do more to mitigate the impact of the U.S. sanctions, especially to sell its oil.

China always believes that the full and effective implementation of JCPOA in accordance with the requirements of the UN Security Council resolutions is the only realistic and effective way to solve the Iran nuclear issue and ease tensions, Geng Shuang, a spokesperson for the Chinese Foreign Ministry, said last Monday.

Noting the U.S. "maximum pressure" against Iran is the root cause of the crisis concerning the Iran nuclear issue, Geng called on all parties to keep calm and restraint and solve problems through dialogue under the Iran nuclear deal joint commission.

Tehran has threatened to take further measures.

It has since exceeded limits the deal had set on its enriched uranium and heavy water stockpiles, as well as passing a cap the deal had imposed on its uranium enrichment.

The 4.5 percent enrichment level it reached is well below the more than 90 percent required for a nuclear warhead.

Iran has yet to specify what further steps it may take, and has repeatedly emphasized that its actions can be reversed "within hours" if European partners deliver on their commitments.

(Cover: The Iranian flag flutters in front the International Atomic Energy Agency headquarters in Vienna, Austria, July 10, 2019. /VCG Photo)