Russian President Vladimir Putin met Iranian Supreme Leader Ayatollah Ali Khamenei in Tehran on Friday after a trilateral summit with Turkey about Syria, Fars News reported.

The summit focused on a looming military operation in the Syrian province of Idlib, the last major stronghold of active opposition to the rule of President Bashar al-Assad, who has received military support from Russia and Iran.

Khamenei told Putin that Syria is a good example of "restraining America", where the Iranian leader said the U.S. has been defeated.

In his meeting last spring with Bashar Assad, Putin had said that the goal in Syria should be peace and foreign forces should leave once that is achieved. Later, Russian officials did not rule out that Putin's words included Iranian and Hezbollah forces.

Ayatollah Khamenei has also told Putin that U.S. sanctions against Russia, Iran and Turkey creates a strong common reason for expanding cooperation; including trade without using the U.S. dollar.

The Iranian economy is facing a crisis as among other things, its national currency has plummeted to historic lows after President Donald Trump announced last May the U.S. withdrawal from the multilateral nuclear agreement with Iran.

Khamenei's comments about an expansion of economic cooperation coincides with tensions among oil producers as Russia and Saudi Arabia have hinted that they can compensate for the dwindling Iranian oil exports. Iran's oil sales are being cut as a result of renewed U.S. sanctions.