Ali Akbar Velayati, a top adviser to Iran’s Leader Ayatollah Seyyed Ali Khamenei, said his meeting with Russian President Vladimir Putin on Thursday had been "very constructive and friendly" and that Moscow would invest in the Iranian oil sector.
"Our leader (Ayatollah Khamenei) values improving ties with Russia as strategic partner ... This path will continue," Velayati said from Moscow.
The Kremlin said Putin and Velayati discussed the situation in Syria and bilateral relations and Velayati had given Putin messages from Ayatollah Khamenei and from President Hassan Rouhani.
Russia, China and the big European powers say they still back a 2015 multinational nuclear deal with Iran, despite US President Donald Trump's decision to pull out and to reimpose economic sanctions on Tehran that were lifted as part of the accord.
"Putin reiterated that Russia rejects America's decision to impose sanctions on Iran ... He said Russia will stand by Iran and will defend Tehran's rights," Velayati said.
Under the 2015 agreement, Iran strictly limited uranium enrichment capacity in exchange for relief from sanctions.
US officials said in June they would push countries to reduce their Iranian oil imports to zero. However, US Secretary of State Mike Pompeo said on Tuesday that Washington would consider requests from some countries to be exempted from sanctions it will put in effect in Nov. 4.
China and India are among the largest importers of Iran’s oil, as well as Turkey and Iraq. In May, India's oil ministry asked refiners to prepare to limit imports of Iranian oil while Turkey said had no intention to halt its oil imports from Iran.
Tehran has been pushing hard to hold output steady amid US sanctions that are expected to hit its exports, pressuring other signatories of the deal to come up with a package of economic measures to salvage the deal.
"Putin said that Russia is prepared to continue its oil investment in Iran at the level of $50 billion. It means Russia is ready to invest this amount in Iran's oil sector," Velayati said.
"This is an important amount that can compensate for those companies that have left Iran (amid US sanctions fear)," Velayati said, in a reference to a number of firms, wary of US sanctions, that have already said they plan to pull out of Iran's market.
He said one of Russia's major oil companies has signed a $4 billion deal with Iran, which he said "will be implemented soon", without elaborating. "Two other major Russian oil companies, Rosneft and Gazprom, have started talks with Iran's Oil Ministry to sign contracts worth up to $10 billion," Velayati added.
Meanwhile, Russian Energy Minister Alexander Novak said on Friday that a deal under which Russia would provide goods to Iran in exchange for oil is still possible.
Russia is studying all legal issues related to the possible deal, he said.
Cooperation in Syria
Velayati said Iran and Russia shared the same view over Syria, where Tehran and Moscow as allies of Syrian President Bashar al-Assad have played decisive roles in turning the tide of war in his favor and in winding down some of the violence.
"Iran and Russia will continue to cooperate in Syria," Velayati said.
He said that Iran would immediately withdraw its "military advisers" from Syria and Iraq only if their governments wanted it to.
"Iran and Russia's presence in Syria will continue to protect the country against terrorist groups and America's aggression ... We will immediately leave if Iraqi and Syrian governments want it, not because of Israel and America's pressure," Velayati said.
"Putin underlined the importance of political and defense cooperation between Iran and Russia in Syria. Soon the presidents of Iran, Russia and Turkey will attend a summit in Tehran," said Velayati, who is expected to visit China shortly. Trump and Putin are expected to discuss Iran's regional role and the Syrian conflict at a summit in Helsinki next Monday.
Velayati touched on the objectives of the Israeli leader's visit to Moscow where he "repeated his delusional and threadbare accusations against Iran."
"The process of developing relations between Iran and Russia is not one-sided and therefore, the irrelevant, meaningless and interventionist claims made by Netanyahu do not affect Iran-Russia relations," he said.
"We hope that the cooperation between Iran and Russia will be a model for cooperation among Iran, China, India and some of the major East Asian countries, helping publicly realize a strategic vision to develop relations with the eastern countries."
Reuters and Press TV contributed to this story.