Delegates attend a meeting of the Joint Commission of the Joint Comprehensive Plan of Action (JCPOA) in Vienna, Austria, on July 28, 2019.  Photo:Xinhua

The remaining parties involved in the faltering Iran nuclear deal were expected to meet in Vienna on Wednesday in their first gathering after Britain, France and Germany launched a dispute process over Tehran's successive pullbacks.

The meeting came as the parties tried to find a way to save the landmark 2015 agreement, which has been crumbling since the US withdrew in 2018 and reimposed crippling sanctions on Iran.

The Europeans hoped to persuade Tehran to come back in line with the deal curbing Iran's nuclear program after Tehran made a series of moves in protest of the US pullout.

Wednesday's meeting at the political directors' level, convening the commission set up by the deal, was expected to be chaired by EU senior official Helga Schmid.

"This is a chance, though not 100 percent, to stop any escalations before it is too late," Russian Foreign Minister Sergei Lavrov was quoted as saying by the Russian Embassy in Vienna on Twitter.

In its last announcement in early January, Tehran said it would not adhere to limits on the number of centrifuges used to enrich uranium as was agreed in the deal.

It was its fifth step away from the deal since US President Donald Trump's withdrawal and led Germany, Britain and France to trigger a dispute process on January 14.

The process outlines several steps, the last one of which is notifying the UN Security Council. UN sanctions would then automatically "snap back" after 30 days unless the Security Council voted to veto it.

A diplomat speaking on the condition of anonymity said that no time table had been fixed for resolution of the dispute, adding "we are still far from a result."

"We all want to save the JCPOA (Joint Comprehensive Plan of Action, as the deal is known by) so that inspectors can continue their work in Iran," the diplomat said, referring to the inspections by the International Atomic Energy Agency.

The Vienna-based UN nuclear agency has been tasked with monitoring the deal's implementation and issues regular reports, which the latest is expected within days.

Western diplomats recognize it will be highly unlikely Iran will heed calls to come back into full compliance without substantial concessions in return - such as an end to US sanctions or Europe taking measures to offset any economic impacts.