Iran said on Monday it would not be dictated to by foreign interests, while Russia stuck to its position of linking the revival of a 2015 nuclear deal to Western sanctions over Ukraine by saying the pact cannot discriminate between participants.
After 11 months of intensive talks between Tehran and world powers in Vienna to revive the nuclear agreement, all parties involved in the negotiations had said an agreement was close.
But on Saturday Russian Foreign Minister Sergei Lavrov said Moscow wanted a guarantee from the United States that its trade, investment and military-technical cooperation with Iran would not be hindered by sanctions imposed since it invaded Ukraine.
Read more: Iran says agreed roadmap with IAEA to resolve nuclear issues
Iran's Foreign Minister Hossein Amirabdollahian said Tehran would not allow "any foreign elements to undermine its national interests", Iran's state media reported on Monday, while the foreign ministry said it awaited an explanation from Russia.
A few hours later, Lavrov told Amirabdollahian in a phone conversation that the revived nuclear deal should not allow for any discrimination between participants.
"It was underscored that the revival of the JCPOA must provide for all participants to have equal rights in relation to the unhindered development of cooperation in all areas, without any discrimination," the Russian foreign ministry quoted Lavrov as saying, using the acronym for the 2015 agreement.
France on Monday warned Russia not to resort to blackmail over efforts to revive the deal.
Oil prices hit their highest since 2008 on Monday amid market supply fears as the United States and European allies considered banning Russian oil imports and prospects for a swift return of Iranian crude to global markets receded.
'Trying it on'
The pact to curb Tehran's nuclear programme in exchange for sanctions relief, was abandoned by the United States under former president Donald Trump in 2018.
Also read: Iranian nuclear talks clouded by Russian demands
Although progress has been made towards restoring it, diplomats told Reuters that several key issues still needed to be resolved in the talks, including the extent to which sanctions on Iran would be rolled back.
Western officials say there is a common interest in avoiding nuclear non-proliferation and are trying to ascertain if what Russia is demanding regards only its commitments to the Iran deal. That would be manageable, but anything beyond that would be problematic, they say.
A French presidency official urged Russia to assess what was at stake in Vienna, "that is to say Iran's return to respecting its obligations under the JCPOA", referring to the 2015 deal by its formal name, the Joint Comprehensive Plan of Action.
"Because otherwise, in reality, it's just blackmail and not diplomacy," he told reporters.
A European diplomat added: "The Russians are really trying it on and the Iranians aren't happy, although of course not saying too much publicly. We're trying to find a way through."
European negotiators have temporarily left the talks as they believe they have gone as far as they can and it is now up to the two main protagonists to agree, three diplomats said.
Iran's top security official, Ali Shamkhani, called on Washington on Monday to make political decisions.
"Priority of Iranian negotiators is to resolve remaining issues that are considered (a) … red line. Rapid access to a strong deal requires new initiatives from all parties," Shamkhani tweeted.
Russia's concerns about the impact of Western sanctions on its dealings with Iran follow a push by senior Iranian officials for deeper ties since hardliner Ebrahim Raisi became president last year.
Iran's top authority, Supreme Leader Ayatollah Khamenei, has called for closer ties with Russia due to his deep mistrust of the United States.