This is stated on the website of the Institute for the Study of War - ISW.
"Russia and Iran have expanded their strategic partnership since Russia invaded Ukraine in February 2022. Senior Russian and Iranian officials have met frequently in recent months to strengthen cooperation and sign economic, as well as military deals. Moscow and Tehran have long cooperated when their interests overlap, particularly in confronting the US in the Middle East, but their latest actions underscore a more concerted effort to strengthen their partnership", it is noted.
Putin and Ebrahim Raisi are known to have spoken at least four times since the start of the invasion - more than they have with most other leaders.
"Putin's visit to Tehran in July 2022 marked his first foreign trip outside the territory of the former Soviet Union since the beginning of the war. These interactions show a deepening and potentially more balanced relationship in which Russia is no longer the dominant party. This partnership is likely to challenge the interests of the US and its allies in Europe, the Middle East, and around the world", the Institute added.
Experts suggest that the deepening of these ties will threaten the interests of the US and its allies in Europe, the Middle East, and the rest of the world. Iranian material support can help Russia in its military gains in Ukraine and Eastern Europe. For its part, the Russian Federation will support Iran's military space program and air force, which will increase the threat to the United States and its partners.
"Increasing Iranian control and influence in Syria will allow the IRGC (Islamic Revolutionary Guard Corps) from Syria to more effectively threaten US military bases in the Middle East and our regional partners such as Israel and Turkey. Finally, Moscow and Tehran will likely use their deepening economic ties to ease US sanctions", ISW emphasized.
In addition, Russian-Iranian ties will affect Ukraine, as Tehran provides weapons and is likely to carry out cyber attacks to support the Russian invasion.
"Iran has agreed to provide Russia with some of its most advanced military drones, such as the Shahed-129 and Shahed-191, for use in Ukraine. On August 5, a senior Ukrainian official said that the Kremlin has so far received 46 drones, while Western media indicated that Iran may provide up to 300 in total", the department added.
It is also known that some Russians are currently in Iran for training in the use of drones.