• "Iranian material support such as drones has kept Putin fighting in Ukraine for much longer than expected. Ballistic missiles will keep him in that fight for longer now," one analyst told CNBC.
• The Fateh-110 missile has an effective range of about 190 miles, is known to be highly accurate, and has been used in strikes from Iran into Iraq, Syria and Pakistan.
• Meanwhile, the future of U.S. military aid for Ukraine looks increasingly uncertain.

Iran has sent hundreds of its powerful ballistic missiles to the government of President Vladimir Putin in Russia, furthering the military cooperation between the two U.S. adversaries, Reuters reported this week, citing a number of unnamed senior Iranian military sources.

The reported transfer of the powerful weapons are set to strengthen Putin's hand in Ukraine as the two-year mark of Russia's full-scale invasion of its neighbor nears. It follows already-documented weapons cooperation between Tehran and Moscow since 2022, particularly with the transfer of Iranian-made Shahed drones that Russian forces have deployed to deadly effect in Ukraine.

Reuters reported that Iran delivered at least 400 of its short-range Fateh-110 ballistic missiles to Russia in January of this year, and that figure is likely to rise. Iran declined to comment to Reuters while Russia did not immediately respond.

"It was always a matter of when, not if, Iran would transfer ballistic missiles to Russia," Behnam ben Taleblu, a senior fellow at the Foundation for Defense of Democracies, told CNBC.

"Iranian material support such as drones has kept Putin fighting in Ukraine for much longer than expected. Ballistic missiles will keep him in that fight for longer now."

In 2022, U.S. Central Command estimated that Iran had over 3,000 ballistic missiles in its arsenal. Iran has in recent years developed advances and upgrades to its Fateh class of missiles improving things like precision, range, lethality, maneuverability, and survivability, analysts say. The Fateh-110 missile has an effective range of 300 kilometers (roughly 190 miles), is known to be highly accurate, and has been used in strikes from Iran into Iraq, Syria and Pakistan.

"Iranian officials have indicated that more missiles are on the way. Iran manufactures the missiles domestically with very little input from foreign sources and can produce them in large numbers for an extended period of time," analysts at political risk consultancy Eurasia Group wrote in a research note.

"The Iranian missiles offer Russia additional capabilities as it presses its advantage against Kyiv amid delays in additional U.S. aid," it said.

Russian gains

Russia has chalked a substantial victory in the eastern Ukrainian city of Avdiivka. It symbolizes a painful loss for Ukraine, and hundreds of Ukrainian troops are feared missing, potentially taken prisoner by Russian forces.

The Russian gains come as continuing U.S. aid for Ukraine becomes far less certain. The U.S. Senate in in mid-February passed a $95 billion aid package for Ukraine, Taiwan, and Israel, with about $60 billion slated for Ukraine, but several Congressional Republicans in the House of Representatives are opposing its passage.

Kyiv and its allies also look ahead with worry to the 2024 U.S. election, as a potential Donald Trump presidency could see Ukraine aid cut entirely.

Trump also threatened to abandon the principle of mutual defense under the NATO treaty for member states who do not dedicate at least 2% of their GDP to defense spending, a figure agreed upon in 2014; he even suggested he'd encourage Russia to attack them.

While this raised alarm and condemnation among leaders of several NATO states, without U.S. support, Europe is severely under-equipped to supply Ukraine with what it needs to withstand Russia's offensive. The U.S. has supplied some $44.9 billion of security assistance to Ukraine, with only Britain coming in as a distant second, to the tune $12 billion.

What does Iran get in return?

Tehran's relationship with Moscow pays off for its government; already heavily sanction by the U.S. and EU, weapons trade with Russia is a valued source of revenue for the Islamic Republic.

FDD's Ben Taleblu describes "reports of cash and gold transfers, Western conventional weapons transfers, fighter jet deals, and even assistance with Iran's space program from Russia. For a risk-tolerant Islamic Republic, the partnership with Russia continues to bear fruit."

Analysts note that several rounds of Western sanctions on Iran, which have helped cripple its economy, have not been enough to deter it from continuing to sell Russia the lethal weapons it uses in Ukraine. It also stands to gain new military hardware itself.

"The missile deal suggests that an agreement is now in place for Russia to send advanced weapons systems to Iran. Russia delivered a squadron of modern training aircraft to Iran's air force in September 2023, the first phase in a deal that also includes SU-35 jet interceptors," Eurasia Group wrote.

The SU-35, Russia's air-defense fighter jet, would provide Iran "with its first modern combat aircraft in decades significantly expanding its capabilities at a time of mounting tensions with Israel and the U.S.," the report said.

In terms of Washington's response, that may be limited – primarily because the Biden administration is reluctant to further escalate tensions in the Middle East. While it can sanction Iran's weapons programs, it can't actually intercept the transporting of the missiles to Russia along its supply route; a U.N. arms embargo that barred Iran from selling its missiles expired in 2023.

The weapons supply boost for Russia while Ukraine's allies appear to stall illustrates what many observers describe as the war's tide shifting in Russia's favor.

"As Washington debates standing with Ukraine, Iran continues to cozy up to Russia," Ben Taleblu said, "marking the furthest reported instance of Iranian ballistic missile proliferation in its history."