Stopping the delivery of munitions and other military aid including air defense systems likely would be a blow to Ukraine as it contends with some of Russia's largest missile and drone attacks of the three-year-old war.

"This decision was made to put America's interests first 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.

The curtailment of military aid signals a possible shift in the priorities of US President Donald Trump, who has pressed for Russia and Ukraine to speed up stalled peace talks.

The Republican has moved on to playing a greater role in orchestrating a possible ceasefire in Gaza and toning down Iran-Israel tensions after a deadly 12-day conflict between the arch foes.

The Pentagon review determined that stocks had become too low on some previously pledged munitions, and that some pending shipments now would not be sent, said a US official who spoke on condition of anonymity, according to Politico, which first reported the halt of military aid.

"The strength of the United States Armed Forces remains unquestioned -- just ask Iran," Kelly said, making a reference to the recent US bombings and missile strikes against the Islamic republic's nuclear facilities.

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

Michael McFaul, who was the US ambassador to Russia from 2012 until just before the Crimea conflict began in 2014, said on X: "The Trump administration is even stopping delivery of Patriots? So disgusting and embarrassing as the 'leader of the free world.' I guess we are done with that."

Last week at a NATO summit in the Netherlands, Ukrainian President Volodymyr Zelensky met with Trump and appeared to get a vague response from the US leader on Patriot air defense systems.

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

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

- Thousands of drones -

A Russian drone attack on Ukraine's Kharkiv region killed one person and wounded another, its governor said early Wednesday.

The attack follows Ukrainian drone strikes which killed three people and wounded dozens in the Russian city of Izhevsk on Tuesday, striking more than 620 miles (1,000 kilometers) from the front line -- one of the deepest attacks inside Russia to date.

An AFP analysis published Tuesday found that Russia dramatically ramped up aerial attacks in June, firing thousands of drones as Ukraine's stretched air defense systems and exhausted civilian population felt the Kremlin's increased pressure.

An April report from the Stockholm International Peace Research Institute (SIPRI) found that Ukraine is being outgunned by Russia, despite spending more of its GDP on defense than any other country in the world.

Ukraine's military expenditure in 2024 was $64.7 billion, SIPRI said, and Kyiv has relied heavily on its allies in Europe and the United States for weapons and aid.

Russian leader Vladimir Putin blamed the West for fanning the flames of war with that support, telling French president Emmanuel Macron Tuesday that the West has "for many years ignored Russia's security interests."

The White House's tone has openly shifted on Ukraine with the Trump presidency.

Back in 2022, then president Joe Biden affectionately embraced Zelensky at the White House as his administration announced another $2 billion in weapons for Ukraine.

During Zelensky's Washington visit earlier this year, he was belittled on-camera by Trump and Vice President JD Vance during an Oval Office meeting, who ganged up to accuse the Ukrainian leader of ingratitude.

Asked by AFP for comment on the halt of shipments and why it was occurring, the Pentagon did not respond directly.

But its chief spokesman Sean Parnell said "America's military has never been more ready and more capable thanks to President Trump and Secretary (Pete) Hegseth's leadership."