US President Donald Trump hailed a "very good" call with Ukraine's Volodymyr Zelensky on Wednesday, a day after Russia's Vladimir Putin agreed to temporarily halt attacks on Kyiv's power plants.

Trump said efforts to secure a full ceasefire in Russia's three-year-old war remained "on track," despite the fact that his call with Putin failed to produce any broader peace deal.

As Kyiv and Moscow accused each other of continuing attacks, Zelensky said after the "frank" call that Ukraine was ready to pause strikes on both Russian energy and civilian infrastructure.

Trump said he spoke for around an hour with his Ukrainian counterpart, their first conversation since they had a blazing televised row in the Oval Office just over two weeks ago.

"Much of the discussion was based on the call made yesterday with President Putin in order to align both Russia and Ukraine in terms of their requests and needs," Trump said on his Truth Social network.

"We are very much on track."

The White House later said that during the call Trump had floated US "ownership" of Ukrainian power plants as it would be the "best protection" for them.

Speaking on RTHK's Hong Kong Today programme, RTHK's Washington correspondent Simon Marks said while Trump was showing American willingness to help Ukraine repair its damaged power infrastructure, it also showcased how transactional his administration is on foreign policy.

"It was another one of those jarring moments at the White House when that was suddenly announced. There had been no indication at all leading up to either of these calls with Vladimir Putin or Volodymyr Zelensky that that was what Donald Trump had in mind... it also indicates that for Donald Trump, so many of these international issues he seems to think can be resolved like a business negotiation."

The billionaire former real estate mogul has already pushed Kyiv into a deal to give the United States preferential access to its critical mineral resources.

Trump also pledged to help Ukraine get more air defence equipment from Europe, a statement from National Security Advisor Mike Waltz and Secretary of State Marco Rubio said.

But while Ukraine has already agreed to a US plan for an unconditional 30-day ceasefire with Russia, Putin is still refusing.

The Kremlin leader insisted during his call with Trump that a full ceasefire was only possible if the West halts its billions of dollars in military aid to Kyiv – Moscow's long-standing demand.

Putin also demanded Ukraine must not be allowed to rearm, and that it must halt mandatory mobilisation. (AFP)