TEHRAN, Iran (AP) – Russian President Vladimir Putin’s visit to Iran starting Tuesday is intended to deepen ties with regional heavyweights as part of Moscow’s challenge to the United States and Europe during its grinding campaign in Ukraine. In only his second trip abroad since Russian tanks rolled into its neighboring country in February, Putin is scheduled to hold talks with Iran’s President Ebrahim Raisi and Turkish President Recep Tayyip Erdogan about some of the most pressing issues facing the region, including the conflict in Syria and a U.N.-backed proposal to resume exports of Ukrainian grain to ease the global food crisis.