The US and Japan struck a deal to make more missiles for Patriots, which have proved crucial in Ukraine

• The US and Japan on Monday announced a deal to expand Patriot missiles.
• Patriot systems have proven effective in Ukraine, countering many Russian air strikes.

The US and Japan agreed to expand production of the Patriot missile systems, putting the spotlight again on a weapon in the ascendancy.

The US-made Patriot missile systems have exceeded expectations in Ukraine, where they have formed a crucial part of Ukrainian air defense.

The Patriot system is a ground-based, surface-to-air missile battery that can take down targets from planes to cruise missiles to drones.

Though it has been through rocky patches, its success against Russia dispelled doubts about its effectiveness, as Business Insider's Sinéad Baker previously reported.

High-level defense talks in Tokyo in recent days further cemented its status, and provided further ways that the US might get Patriot stock for Ukraine via its Japanese ally.

The US-Japan Security Consultative Committee released a joint statement after the talks, committing to "high-priority efforts" to produce more ammo for Patriots.

The statement also said that work was underway to transfer existing Patriot ammo from Japan to the US, which could, in turn, free up stocks for Ukraine.

However, there could be problems making good on the ambitions of the partnership.

Per a report by Reuters earlier this month, Japan has a shortage of parts which limits its ability to make more Patriot ammunition.

The missing part is produced by Boeing back in the US, per Reuters — which could mean the true bottleneck remains with a US company.

The Reuters report, citing an unnamed official, said it could be as long as 2027 before Boeing can enhance its own production and resolve the issue.

At the Tokyo talks the US and Japan also moved to strengthen their alliance against China, whose rise they described as their "greatest strategic challenge".