Ukraine summoned a senior US diplomat on Wednesday, urging its key ally not to cut or delay critical military aid after the White House said it was halting some weapons shipments.

Kyiv said it had not been told anything by the United States about the halt to aid, which could thwart its ability to fend off escalating Russian air attacks.

Moscow revelled in the decision, saying it could bring the end of the war closer.

Kyiv has long feared halts to US aid after Donald Trump returned to the White House in January, having criticised the tens of billions of dollars in support and weapons sent by his predecessor, Joe Biden.

The US embassy's deputy chief of mission, John Ginkel, was summoned on Wednesday -- a rare diplomatic move usually reserved for foes and rivals, not vital allies -- amid uncertainty about what the cuts would mean for Kyiv.

"The Ukrainian side stressed that any delay or procrastination in supporting Ukraine's defence capabilities would only encourage the aggressor to continue the war," Ukraine's foreign ministry said in a statement.

The White House announced Tuesday it was halting some key weapons shipments to Ukraine promised by the previous US administration, but did not provide details on what would be cut.

Under Biden, Washington had spearheaded Western support for Ukraine, with Congress having approved more than $100 billion in aid, including $43 billion in weaponry.

Trump, who has held several phone calls with Russian President Vladimir Putin and pushed the two sides into peace talks, has refused to announce new packages and Kyiv has been corralling Washington's European allies to step up support for when US deliveries end.

Putin has rejected calls for an immediate and unconditional ceasefire and demanded Ukraine cede more territory if it wants Moscow to halt its invasion.

Tens of thousands have been killed since February 2022 when Russia invaded, with millions forced to flee their homes and swathes of eastern and southern Ukraine destroyed.

'Seriously dependent'

A senior Ukrainian military official raised concerns about the impact of the weapons halt to AFP.

"We are now seriously dependent on American arms supplies, although Europe is doing its best, but it will be difficult for us without American ammunition," a high-ranking source in the Ukrainian military said, speaking on condition of anonymity.

In Moscow, the Kremlin said reducing the flow of weapons to Kyiv will help end the conflict faster.

"The fewer the number of weapons that are delivered to Ukraine, the closer the end of the special military operation," Kremlin spokesman Dmitry Peskov told reporters in response to a question by AFP, using Russia's term for its more than three-year offensive.

The US decision was taken"following a DOD (Department of Defense) review of our nation's military support and assistance to other countries across the globe," White House Deputy Press Secretary Anna Kelly told AFP in an email.

Kyiv said it was caught off-guard by the move.

"Ukraine has not received any official notifications about the suspension or revision of the delivery schedules for the agreed defence assistance," the defence ministry said.

"The path to ending the war lies through consistent and joint pressure on the aggressor, as well as through continued support for Ukraine," it added.

"We are clarifying the situation. I think that everything will be clarified in the coming days," presidential aide Dmytro Lytvyn told reporters.

Politico and other US media reported that missiles for Patriot air defence systems, precision artillery and Hellfire missiles are among the items being held back.

Last week at a NATO summit in the Netherlands, Ukrainian President Volodymyr Zelensky met with Trump, who gave no public indication he was thinking of cutting aid.

"We're going to see if we can make some available," Trump said of the air defence missiles that Kyiv desperately seeks to shoot down Russian attacks.

"They're very hard to get," Trump added.

Russia has ramped up attacks on Ukraine in June, launching nearly twice as many missiles and over 30 percent more drones than in May, according to an AFP analysis of Ukrainian air force data.

(FRANCE 24 with AP)

The US is halting some shipments of weapons to Ukraine amid concerns that its own stockpiles have declined too much, officials said Tuesday, a setback for the country as it tries to fend off escalating attacks from Russia.

Kyiv reacted to the delay in military aid on Wednesday by summoning the deputy chief of the US embassy in Kyiv to a meeting Wednesday and warned him any delays in US military aid to Ukraine would"encourage" Russia, the foreign ministry said.

"John Ginkel was invited to the Ukrainian foreign ministry... The Ukrainian side stressed that any delay or procrastination in supporting Ukraine's defence capabilities would only encourage the aggressor to continue the war," the ministry said in a statement.

Certain munitions were previously promised to Ukraine under the Biden administration to aid its defences during the more than three-year-old war. The pause reflects a new set of priorities under President Donald Trump and came after Defence Department officials scrutinised current US stockpiles and raised concerns.

“This decision was made to put America’s interests first following a review of our nation’s military support and assistance to other countries across the globe,” White House spokesperson Anna Kelly said in a statement. “The strength of the United States Armed Forces remains unquestioned – just ask Iran.”

That was a reference to Trump recently ordering US missile strikes against nuclear sites in Iran.

The Pentagon review determined that stocks were too low on some weapons previously pledged, so pending shipments of some items won’t be sent, according to a US official who spoke on condition of anonymity to provide information that has not yet been made public.

The Defence Department did not provide details on what specific weapons were being held back.

“America’s military has never been more ready and more capable,” spokesman Sean Parnell said, adding that the major tax cut and spending package moving through Congress “ensures that our weapons and defence systems are modernised to protect against 21st century threats for generations to come".

The halt of some weapons from the US is a blow to Ukraine as Russia has recently launched some of its biggest aerial attacks of the war, in an escalating bombing campaign that has further dashed hopes for a breakthrough in peace efforts championed by Trump. Talks between the sides have ground to a halt.

The US stoppage was first reported by Politico.

To date, the US has provided Ukraine more than $66 billion worth of weapons and military assistance since Russia invaded its neighbour in February 2022.

Over the course of the war, the US has routinely pressed for allies to provide air defence systems to Ukraine. But many are reluctant to give up the high-tech systems, particularly countries in Eastern Europe that also feel threatened by Russia.

Trump met with Ukrainian leader Volodymyr Zelensky on the sidelines of the NATO summit last week and had left open the possibility of sending Kyiv more US-made Patriot air defence missile systems, acknowledging they would help the Ukrainian cause.

“They do want to have the antimissile missiles, OK, as they call them, the Patriots,” Trump said then. “And we’re going to see if we can make some available. We need them, too. We’re supplying them to Israel, and they’re very effective, 100% effective. Hard to believe how effective. They do want that more than any other thing.”

Those comments reflect a change of thinking about providing weapons to Ukraine across the administration in recent months.

In testimony before lawmakers in June, Defence Secretary Pete Hegseth said he has moved quickly to quash wasteful programmes and redirect funding to Trump’s top objectives.

Hegseth said a negotiated peace between Russia and Ukraine, which has been promoted for months by Trump, makes America look strong, even though Moscow is the aggressor in the conflict. He also said the defence budget includes hard choices and “reflects the reality that Europe needs to step up more for the defence of its own continent. And President Trump deserves the credit for that.”

The defence secretary told lawmakers last month that some US security spending for Ukraine was still in the pipeline, without providing details. But he said such assistance – which has been robust for the past two years – would be reduced.

“This administration takes a very different view of that conflict,” Hegseth said. “We believe that a negotiated peaceful settlement is in the best interest of both parties and our nation’s interests.”

The change comes after Hegseth skipped a meeting last month of an international group to coordinate military aid to Ukraine that the US created three years ago. Hegseth’s predecessor, Lloyd Austin, formed the group after Russia attacked Ukraine, and Hegseth's absence was the first time the US defence secretary wasn’t in attendance.

Under Austin’s leadership, the US served as chair of the group, and he and the chairman of the Joint Chiefs of Staff attended monthly meetings, which were both in person and by video.

Hegseth had previously stepped away from a leadership role of the Ukraine Defense Contact Group – turning that over to Germany and the United Kingdom – before abandoning the gathering altogether.