Originally Published: 19 JUL 22 11:57 ET

By Rob Picheta, Anna Chernova, Uliana Pavlova and Chris Liakos, CNN

(CNN) -- Russian President Vladimir Putin arrived in Iran on Tuesday for his first international trip beyond the borders of the former Soviet Union since he launched Russia's invasion of Ukraine in February.

Putin met with Iranian President Ebrahim Raisi in Tehran, and was also scheduled to hold discussions with Turkish President Recep Erdogan.

It is just his second trip outside Russia since he ruptured the country's ties with the West by launching his invasion of Ukraine. Putin visited Tajikistan and Turkmenistan, both former Soviet nations in central Asia, last month.

The visit comes amid Ukrainian claims that more than 20 million tons of grain remain stuck in Ukraine due to the Russian blockade of various Black Sea ports. Putin and Erdogan are set to discuss the issue of exporting grain from Ukrainian ports, the Kremlin said ahead of the trip, according to state news agencies RIA Novosti and TASS.

"The work is very active. You know that on July 13, the first four-party meeting on grain was held in Istanbul with the participation of representatives of Russia, Ukraine, Turkey and the UN. We are ready to continue work on this track, this work will be continued," aide to the Russian President, Yury Ushakov, said at a briefing as quoted by RIA.

His trip to Iran will see him meet face-to-face with Erdogan, the leader of NATO member Turkey, and comes after the Erdogan repeated his threat to block the ascension of Sweden and Finland to the alliance after conditionally agreeing to green light their bid in June.

"I would like to remind you once again that we will freeze the process if they do not take the necessary steps to fulfill our conditions," Erdogan said Monday after a cabinet meeting. He lifted his opposition to the expansion at a NATO summit last month -- a major diplomatic breakthrough that provided a blow to Putin.

Meanwhile, Putin's relationship with Iran has alerted Western officials as he prepares to ramp up ground offensives in eastern Ukraine following his troops' capture of the Luhansk region.

Recently declassified US intelligence indicates that Iran is expected to supply Russia with "hundreds" of drones -- including weapons-capable drones -- for use in the war in Ukraine, with Iran preparing to begin training Russian forces on how to operate them as early as late July, according to White House officials.

"Russia turning to Iran for the help speaks volumes about the degree to which both nations, for their actions into different areas of the world, have been increasingly isolated by the international community," the National Security Council coordinator for strategic communications John Kirby told CNN last week.