“Russia has taken important steps in this area. Now there’s a very good opportunity for new steps on your part,” Rouhani told Putin, speaking in Persian. He did not elaborate.

Iranian diplomats are expected to hold talks with members of the P5+1 group of international negotiators – China, France, Germany, Russia, United Kingdom, United States – on the sidelines of the UN General Assembly later this month.

Western countries allege that Iran may be developing nuclear weapons under the guise of a peaceful nuclear program. Russia – which built Iran’s Bushehr nuclear reactor – has proposed in the past various technical measures to increase the transparency of Iran’s nuclear research, which Tehran insists is for purely peaceful purposes.

Russian newspaper Kommersant reported Wednesday that Putin and Rouhani also plan to discuss a contract for Russia to construct a second unit at the Bushehr nuclear plant, but a spokesman for Putin said the matter was not mentioned Friday.

Putin also avoided specifying any concrete proposals on Iran’s nuclear program in his speech after the talks, saying only that “we know to what extent international affairs turn upon the Iranian nuclear problem.”

“But we in Russia know also that Iran is our neighbor, a good neighbor. You don’t choose your neighbors, and we had cooperated, are cooperating and definitely will cooperate a lot,” Putin said.

Putin will travel to Iran “on the first opportunity,” his spokesman also said, adding that the date was not set. News reports have claimed the Russian leader planned to travel to Iran during his tour of Caspian nations in August, but the visit never materialized, which Russian media attributed to Moscow and Tehran failing to agree on the exact venue for the visit.

Neither president also made any mention of a possible deal to deliver to Iran state-of-the-art Antei-2500 air defense missile systems in replacement for previously ordered S-300 systems. A contract for S-300 was unilaterally scrapped by Moscow following a new round of international sanctions against Tehran in 2010.

Kommersant reported last summer that the Kremlin was considering supplying the Antei-2500 to Tehran in exchange for Iran dropping a $4 billion lawsuit that it launched against Russia in an international court in Geneva after Russia suspended the S-300 deal. Russian and Iranian officials have denied talks on the Antei-2500, though Russian lawmakers spoke on Wednesday of the possibility of stepping up deliveries of unspecified “defense weapons” to Iran if the United States proceed with airstrikes against Syria.