VIENNA: The signatories to the Iran nuclear deal said Tuesday that they stood by the faltering accord and China slammed US efforts to restore international sanctions on the Islamic republic and extend an arms embargo.

Britain, France, Germany, China and Russia are struggling to save the landmark 2015 accord with Iran, which has been progressively stepping up its nuclear activities since the United States pulled out of the deal in 2018.

Tehran insists it is entitled to do so under the terms of the accord - which swapped sanctions relief for Iran's agreement to scale back its nuclear programme - following Washington's withdrawal and reimposition of sanctions.

EU senior official Helga Schmid, who chaired the talks in Vienna on Tuesday, wrote on Twitter that the meeting's participants were "united in resolve to preserve the #IranDeal and find a way to ensure full implementation of the agreement despite current challenges".

Representatives from Britain, China, France, Germany, Iran and Russia all attended the talks - part of a regular series of gatherings to discuss the accord, which have been increasingly tense since the US pullout began unravelling the agreement.

China's representative, senior Foreign Ministry official Fu Cong, told reporters after the meeting that Iran needed to come back to full compliance, but at the same time "the economic benefit that is due to Iran needs to be provided".