Iran aided Russia against Ukraine. Now it needs to call in the favor

Iran has been one of Russia's few staunch allies throughout the war against Ukraine, but Tehran now faces the strain of indirectly fighting its nemesis Israel on two fronts.

Under pressure — but still defiant — Iran could start looking to Russia for help, given its need for greater air defense capabilities and military intelligence to detect a highly-anticipated but yet-to-materialize direct Israeli attack on Iran, analysts told CNBC.

Russia is well-positioned to provide Tehran with such capabilities, but the extent to which it will assist the Islamic Republic remains uncertain.

"I fully expect that the Iranians have high expectations of the Russians to provide them with something," Bilal Y. Saab, associate fellow in the Middle East and North Africa Programme at think tank Chatham House, told CNBC Thursday, noting that reputation is of the utmost importance in international relations — even among authoritarian countries.

"So if the Russians are going to bail on this, it's going to have consequences with regards not only to its relationship with the Iranians, but to any other partner, such as the Chinese," he said.

"They've got to maintain some kind of reputation that they are good for it, and so I have medium-to-high expectations that they would actually provide them with what they need. Now, whether they provide them with everything they need, this is what nobody knows."

Russia is unlikely to offer military intervention against Israel on behalf of the Iranians, Saab said, given it is already "too bogged down in Ukraine."

"It's also too risky of a game to go against the United States over the Iranians ... so I think that [it's] more likely they would stay on the sidelines and try to help from as far away as possible," he said.