Ukraine's ability to strike deep into the heart of Russian territory to target supply lines and infrastructure could mean the difference between an ongoing war and the end of Vladimir Putin's invasion.
Despite no official comment from the White House, widespread reports in the United States claim the Biden administration will allow Ukraine's army to use long-range missile weapons supplied from the US.
What this means for Russia's war in Ukraine, which will enter its third year in February, is still up in the air.
Why has Biden done this now?
Ukraine has been calling for permission for two years to use the long-range US system called the Army Tactical Missile Systems, known colloquially as ATACMS.
These missiles have a range of about 300 kilometres, meaning strikes inside Russian territory would be possible at a level far greater than present Ukrainian capacity.
George Barros, a lead analyst on Russia and Ukraine at the US Institute for the Study of War, said the deployment of North Korean troops to the front lines in Kursk was a "major escalation" of Russia's invasion that pushed the US towards allowing its missiles to be used.
"The Western response [to the deployment] was really pitiful … And so I do believe that the response that the administration is leading here is, you know, it's the beginning of something."
The looming second presidency of Donald Trump is another factor in President Joe Biden's mind, Mr Barros said.
Trump has previously said he could "end the war in one day" and has criticised the level of funding Ukraine has received from the US.
The Biden government has sent more than US$64.1 billion in military aid since the invasion began in February 2022, according to the US Department of State.
"I think Biden and his advisors are trying to essentially do what they can do while they still hold the reins of power in government, before they give it back to president-elect Trump in January," Mr Barros said.
Mr Barros said Biden's policies in Ukraine would form part of his legacy, and this move, while overdue, was part of a decision to shore that up.
What could the missiles target?
It's not yet clear if the US will give Ukraine an open slate to target any Russian infrastructure, or if they will be required to make only "surgical" strikes against specific Russian military targets, Mr Barros said.
However, a greater goal for the use of the long-range systems would be targeting Russia's military supply network in its entirety.
"So this is a part of response to that major escalation of the war against Ukraine. But really, if anything, the North Koreans provided convenient timing," Mr Barros said, for Ukraine to finally target Russia's "vulnerable underbelly".
This is the logistical framework that the Russian army uses to make its war happen — the supply lines, logistics hubs, communication equipment and other networks that get food, fuel and ammunition to the frontline.
"You really do start to chop off a military at its knees or at his ankles, and you degrade the frontline forces," Mr Barros said, detailing the longstanding need for Ukraine to target these kinds of structures in order to stop Russia's advance.
How could this affect the war?
Ukrainian President Volodymr Zelenskyy called for further support for his country in a video address posted to X on Monday, local time, as he hinted at approval from the US to use the long-range missiles.
"There's been much said in the media today that we have received approval to take relative actions. But strikes are not carried out with words," he said.
"These things are not announced. The missiles will speak for themselves."
Ukraine is reeling from one of the largest strikes on its cities of late after Russian drones and missiles hit the Mykolaiv, Lviv, Kherson, Dnipropetrovsk and Odesa regions on Sunday, killing at least 11 people, as Russian attacks repeatedly target civilian infrastructure such as the power grid.
Stephan Fruehling from the Strategic and Defence Studies Centre at ANU said no one military system or asset would turn the tide at this point in the war, but rather it was about "slowly grinding down" the Russian air defence systems, which were under significant stress.
"It'll be marginal, but things at the margin help," he said.
However, Professor Fruehling said the slow lead-up and media speculation about Biden's decision means the Russian military has had months to get ready for it, including time to move aircraft and other infrastructure out of the range of the missiles.
"These missiles don't exist in huge numbers, and Russia has had time to prepare," he said while noting some American systems turned out to be less effective than hoped, including ATACMS.
"By this point in time, it's a matter of degrees, not something that will cause on its own a significant collapse and put the Russian war machine in danger."
