Iran has attempted to strengthen its ties with Russia after three of its navy ships arrived in Moscow's territorial waters Sunday to commence exercises aimed at building military cooperation between the two countries. The warships, known as the Joshan, Peykan and Damavand, docked in the southern port of Astarakhan for what will be a 12-day stay, according to the Russian news site Sputnik Monday. 

After docking in Astrakhan, the vessels will head to Baku, capital of the Azerbaijan, and then will return home to Iran within two weeks, Ahmad Reza Bagheri, an Iranian Navy captain, told Fars New Agency.

The visit represents growing political and military ties between Tehran and Moscow that have become stronger since the Iran nuclear deal was agreed in July. While the U.S. was a leading country in establishing acceptable conditions for the deal to go through, the Pentagon is likely to be wary of the developing relationship and what it means for the Middle East, where both Moscow and Tehran are heavily involved in conflicts in Yemen and Syria, respectively. 

Earlier this year, to reward Tehran for making progress on the deal that is supposed to prevent the Middle Eastern country from developing nuclear weapons, Russia sanctioned the sale of its S-300 advanced missile system, which had been agreed years before but put on hold because of sanctions. 

Russian ships had previously visited Iran in August, docking at the Anzali port to stage joint military drills. Before that, Iranian ships visited Russian waters in June 2013. Iran announced Sunday's visit earlier this month, declaring that the Damavand, Tehran most advanced warship would be present. 

"Destroyer Damavand will be sent to Russia in the form of a flotilla of warships,” Commander of Iran’s Northern Naval Fleet Admiral Afshin Rezayee Haddad told Russia Today in August.