Russian President Vladimir Putin will discuss the Syria crisis and energy cooperation with Iranian President Hassan Rouhani and Iran's top authority supreme leader Ayatollah Ali Khamenei when he visits Tehran on Wednesday, the Kremlin said on Tuesday.

"Syria-related issues will be on the agenda of the Russian-Iranian bilateral talks," Kremlin spokesman Dmitry Peskov told a conference call with reporters. He did not elaborate.

Russia and Iran are two major backers of the Assad regime in the Syrian conflict.

In March 2011, Syrians were emboldened enough to raise their voice against Assad's dictatorship. However, the regime's response was not as peaceful as protesters expected and the country was subsequently dragged into a deadly civil war after opposition groups took up arms against the regime.

The Syrian civil war has caused the deaths of more than 400,000 people with at least 100,000 still missing. The war has also left nearly 10 million people displaced.

Putin will also hold trilateral talks with Rouhani and lham Aliyev, the president of Azerbaijan, during his working visit to Tehran, Peskov said.