MOSCOW: The Kremlin confirmed on Tuesday that an oil-for-goods barter deal between Russia and Iran was being implemented and officials said the road was clear for Moscow to supply an advanced S-300 anti-missile system to Tehran.

Oil and commodities traders contacted by Reuters were skeptical the barter deal was underway, saying they had not seen any volumes of Iranian oil or Russian grain connected to such a deal being shipped so far.

The latest statements from Moscow coincide with politically sensitive negotiations on a final accord between Iran and the United States, Britain, France, Russia, China and Germany on Tehran’s disputed nuclear program.

Russia has moved quickly to cement ties with Iran after an interim deal was reached this month on curbing the Islamic republic’s nuclear program in exchange for removing economic sanctions.

President Vladimir Putin lifted a self-imposed ban on delivering the air defense system to Iran on Monday, a move to secure a foothold for Russian companies in a much-needed new market after the West imposed sanctions on Russia over Ukraine.