Russia's foreign minister said on Thursday that Moscow was ready to do a deal on its war in Ukraine after US President Donald Trump urged Russian leader Vladimir Putin to halt attacks, in a rare rebuke following the deadliest strikes on Kyiv in months.

"We are ready to reach a deal, but there are still some specific points...which need to be fine-tuned, and we are busy with this," Sergei Lavrov said in an interview with CBS News.

He added the US president was "probably the only leader on Earth who recognised the need to address the root causes of this situation", but said Trump "did not spell out the elements of the deal".

The American president, however, issued a direct appeal to Putin following missile and drone strikes on the Ukrainian capital early on Thursday which left at least 12 people dead.

It was the latest in a wave of Russian aerial attacks that have killed dozens of civilians, defying Trump's push to bring about a rapid end to the bloodshed.

"I am not happy with the Russian strikes," Trump said on social media. "Not necessary, and very bad timing. Vladimir, STOP!"

Trump, who is accused of favouring Russia and has often vilified Ukrainian President Volodymyr Zelensky, was asked by reporters what concessions Moscow had offered in negotiations to end the war.

"Stopping taking the whole country – pretty big concession," he replied. (AFP)