Ukraine appealed to the United States for clarity on Wednesday after it was caught off guard by a White House announcement that Washington was halting some arms shipments to the war-battered country.

The Ukrainian defence ministry, which is deeply dependent on US arms, said it had not been notified about the reduction in aid announced one day earlier.

Moscow revelled in the decision, saying it could bring the end of the war closer. Any slowdown in US support could harm Kyiv's ability to fend off escalating Russian aerial bombardments or frontline gains.

Kyiv has long feared halts to US aid after President 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.

Ukrainian President Volodymyr Zelensky said in an evening address that Kyiv and Washington were clarifying details on supplies.

"Continued American support for Ukraine, for our defence, for our people is in our common interest," he said.

John Ginkel, the deputy chief of mission at the US embassy in Kyiv, was summoned by the foreign ministry – a rare diplomatic move usually reserved for foes and rivals, not vital allies – given uncertainty about what the cuts would mean for Kyiv.

"Now is not the time for weak decisions," Ukraine's Foreign Minister Andriy Sybiga wrote on X. "We need more interceptors and systems. We are also ready to purchase or rent them," he added.

US officials downplayed the move.

"The Department of Defense continues to provide the president with robust options regarding military aid to Ukraine, consistent with his goal of bringing this tragic war to an end," Pentagon spokesman Sean Parnell told journalists.

"The department is rigorously examining and adapting its approach towards achieving this objective while also preserving US military readiness and defense priorities," he said.

In Moscow, the Kremlin said that reducing weapons deliveries to Kyiv would help end the conflict.

"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-long offensive. (AFP)