• A UN Security Council resolution passed in the days after the 2015 Iran nuclear deal has expired.

• That could lead Russia to seek ballistic missiles from Iran as it steps up its attacks on Ukraine.

• Iran has yet to provide those missiles to Russia, but their defense relationship has been expanding.

Russian President Vladimir Putin and Iranian President Ebrahim Raisi .

The day before UN restrictions on Iran's import and export of ballistic missiles and armed drones expired on October 18, Russia declared it was no longer legally obligated to adhere to such restrictions.

The declaration suggests Moscow may seek to refill its stocks with Iranian-made ballistic missiles. That could have ramifications for Ukraine, which is preparing for another winter of Russian missile and drone attacks on civilian and military infrastructure.

An expired remnant of the Iran nuclear deal may help Russia rearm for another winter of missile attacks on Ukraine.

UN Security Council Resolution 2231 was passed in July 2015, days after the US and Iran agreed on the Iran nuclear deal. (The EU, the UK, France, Germany, Russia, and China also signed the deal.) The resolution prohibited Tehran from exporting and importing missiles and drones with ranges exceeding 186 miles and payloads over 1,100 pounds — limits suggested by the Missile Technology Control Regime — until October 2023.

The US and the European signatories of the nuclear deal have decided to uphold sanctions against Iran's missile program, primarily because Tehran violated some terms of the agreement after Washington withdrew in 2018. They were also angered by Iran's decision to arm Russia with Shahed-131 and -136 one-way attack drones.

There has been persistent speculation about Iran supplying Russia with short-range ballistic missiles, or SRBMs, but that would almost certainly draw snapback sanctions under the resolution and Tehran has not yet done so. (While the ballistic-missile ban has expired, previous multilateral sanctions could be reimposed under a sunset clause option outlined under 2231, which remains in effect until 2025.)

Nevertheless, the Russian Foreign Ministry's statement on October 17 suggests Moscow may seek Iranian short-range ballistic missiles to bolster its arsenal for another winter of attacks on Ukraine.

"Supplies to and from Iran of products falling under the Missile Technology Control Regime no longer require prior approval by the UN Security Council," the statement said.

Russia continues to produce its own missiles and drones, but its constant attacks on Ukraine have strained its supplies. Last winter, when Moscow began using Iran's drones, it launched 1,000 of them over six months, and Russian forces launched an estimated 500 drones against Ukrainian targets in September alone, a new record.

If Moscow gets Iranian SRBMs now, Ukraine could face unprecedented pressure, but there are still doubts those missiles will end up in Russian hands.

"Frankly, I don't think that the lifting of final sanctions under the UN resolution will greatly affect the possibility of Iranian ballistic missiles being supplied to Russia," said Anton Mardasov, a non-resident scholar with the Middle East Institute's Syria program.

While Moscow requires "as many high-precision weapons" as possible, it also "doesn't want to become completely dependent" on Tehran, Mardasov told Business Insider. The Russians are also hesitant to antagonize Israel or Arab Gulf countries by forging a strategic military alliance with their main regional rival.

"Unexpected decisions are possible, but for now, I am skeptical about the possibility of Iran supplying the Zolfaghar SRBM and other missiles to Russia," Mardasov said, naming an Iranian missile with a range of just over 400 miles.

Resolution 2231's ban on Iran importing or exporting arms expired in October 2020. Since then, especially after the war in Ukraine began in February 2022, there have been indications that Iran expected to receive two dozen Su-35 fighter jets from Russia. Iran may also hope that in return for exporting drones to Russia and helping build them there, Moscow will license the production of other Russian military hardware in Iran.

Despite "political games" involved in the Su-35 contract, Mardasov expected it to be implemented "in the medium- or even long-term" but said Moscow was less likely to export armored vehicles or helicopters to Iran due to demand on its defense industry to replenish Russian military stocks.

Russia acknowledged in October that the war is straining its arms industry, with its own military's needs being prioritized. Accordingly, Moscow has proposed a new format for arms exports, including more substantial technology transfers.

The head of Russian state arms firm Rosoboronexport said on October 19 that technology partnership contracts with foreign countries will offer "opportunities to launch full-scale production on their territory and develop their own industrial base."

Rosoboronexport has long licensed Indian production of a tailor-made version of the Su-30 fighter, the Su-30MKI. There have been reports of Iranian interest in manufacturing Su-30s under license. Tehran may also want to build later-model T-72 and T-90 tanks under license.

Farzin Nadimi, a defense and security analyst at the Washington Institute for Near East Policy, said "a series of technological exchanges" with Russia is Tehran's "preferred method" but one which Moscow hasn't previously offered.

"Iran has long dreamt of its own fighter jet and main battle tank production lines, but whether such a perceived cooperation will extend to missile/rocket technology, we will have to wait and see," Nadimi told Insider.