Biden approved delivery of the long-range Army Tactical Missile System, known as ATACMS, in February, and then in March the US included a “significant” number of them in a US$300 million aid package announced, officials said.

US officials would not provide the exact number of missiles given last month or in the latest aid package, which totals about US$1 billion.

Ukraine has been forced to ration its weapons and is facing increasing Russian attacks. Ukraine had been begging for the long-range system because the missiles provide a critical ability to strike Russian targets that are farther away, allowing Ukrainian forces to stay safely out of range.

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Information about the delivery was kept so quiet that lawmakers and others in recent days have been demanding that the US send the weapons – not knowing they were already in Ukraine.

For months, the US resisted sending Ukraine the long-range missiles out of concern that Kyiv could use them to hit deep into Russian territory, enraging Moscow and escalating the conflict.

That was a key reason the administration sent the mid-range version, with a range of about 160km (roughly 100 miles), in October instead.

Admiral Christopher Grady, vice-chairman of the Joint Chiefs of Staff, said on Wednesday that the White House and military planners looked carefully at the risks of providing long-range fires to Ukraine and determined that the time was right to provide them now.

He said that long-range weapons will help Ukraine take out Russian logistics nodes and troop concentrations that are not on the front lines.

Grady declined to identify what specific weapons were being provided but said they will be “very disruptive if used properly, and I’m confident they will be”.

Like many of the other sophisticated weapons systems provided to Ukraine, the administration weighed whether their use would risk further escalating the conflict.

The administration is continuing to make clear that the weapons cannot be used to hit targets inside Russia.

At the State Department, spokesman Vedant Patel said on Wednesday that Biden directed his national security team to send the ATACMS specifying that they be used inside Ukrainian sovereign territory.

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“I think the time is right, and the boss (Biden) made the decision the time is right to provide these based on where the fight is right now,” Grady said Wednesday. “I think it was a very well considered decision, and we really wrung it out – but again, any time you introduce a new system, any change – into a battlefield, you have to think through the escalatory nature of it.”

Ukrainian officials haven’t publicly acknowledged the receipt or use of long-range ATACMS. But in thanking Congress for passing the new aid bill Tuesday, Ukrainian President Volodymyr Zelensky noted on the social platform X that “Ukraine’s long-range capabilities, artillery and air defence are extremely important tools for the quick restoration of a just peace”.

One US official said the Biden administration warned Russia last year that if Moscow acquired and used long-range ballistic missiles in Ukraine, Washington would provide the same capability to Kyiv. The official spoke on condition of anonymity to talk about internal discussions.

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Satellite imagery suggests North Korea is supplying Russia with weapons through Rason port

Satellite imagery suggests North Korea is supplying Russia with weapons through Rason port

Russia got some of those weapons from North Korea and has used them on the battlefield in Ukraine, said the official, prompting the Biden administration to greenlight the new long-range missiles.

The US had refused to confirm that the long-range missiles were given to Ukraine until they were actually used on the battlefield and Kyiv leaders approved the public release.

One official said the weapons were used early last week to strike the airfield in Dzhankoi, a city in Crimea, a peninsula that Russia seized from Ukraine in 2014. They were used again overnight east of the occupied city of Berdyansk.

Videos on social media last week showed the explosions at the military airfield, but officials at the time would not confirm it was the ATACMS.

Ukraine’s first use of the weapon came as political gridlock in Congress had delayed approval of a US$95 billion foreign aid package for months, including funding for Ukraine, Israel and other allies.

Facing acute shortages of artillery and air defence systems, Ukraine has been rationing its munitions as US funding was delayed.

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With the war now in its third year, Russia used the delay in US weapons deliveries and its own edge in firepower and personnel to step up attacks across eastern Ukraine. It has increasingly used satellite-guided gliding bombs – dropped from planes from a safe distance – to pummel Ukrainian forces beset by a shortage of troops and ammunition.

The mid-range missiles provided last year, and some of the long-range ones sent more recently, carry cluster munitions that open in the air when fired, releasing hundreds of bomblets rather than a single warhead. Others sent recently have a single warhead.

One critical factor in the February decision to send the weapons was the US Army’s ability to begin replacing the older ATACMS.

The US Army is now buying the Precision Strike Missile, so is more comfortable taking ATACMS off the shelves to provide to Ukraine, the official said.

At the White House, Sullivan said the administration “has worked relentlessly to address those concerns” and stocks are now coming off the production line and the ATACMS can be sent without hurting US military readiness.