Ukrainian President Volodymyr Zelensky said he discussed air defences in a conversation with U.S. President Donald Trump on Friday, and agreed to work on increasing Kyiv's capability to "defend the sky" as Russian attacks escalate.

He added in a message on Telegram that he discussed joint defence production, as well as joint purchases and investments with the US leader.

Ukraine has been asking Washington to sell it more Patriot missiles and systems that it sees as key to defending its cities from intensifying Russian air strikes.

A decision by Washington to halt some shipments of weapons to Ukraine prompted warnings by Kyiv that the move would weaken its ability to defend against Russia's airstrikes and battlefield advances. Germany said it is in talks on buying Patriot air defence systems to bridge the gap.

One source briefed on the call told Reuters they were optimistic that supplies of Patriot missiles could resume after what they called a "very good" conversation between the presidents.

US outlet Axios reported, citing unnamed sources, that the call lasted around 40 minutes, and that Trump told Zelensky he would check what US weapons due to be sent to Ukraine, if any, had been put on hold.

Zelensky, speaking later in his nightly video address, said he and Trump had agreed to "arrange a meeting between our teams to strengthen air defences.

"We had a very detailed discussion on joint production. We need it, America needs it."

The conversation came a day after Trump said he had a disappointing call with Russian President Vladimir Putin.

Russia pummelled Kyiv with the largest drone attack of the war across the capital, hours after Trump's conversation with Putin on Thursday.

Zelensky called the attack "deliberately massive and cynical." (Reuters)