The Kremlin threatened to pull out of peace talks last night after accusing Ukraine of attempting to assassinate Vladimir Putin.

Foreign minister Sergei Lavrov said Russia's negotiating position would change as a result of the alleged Ukrainian drone attack on a state mansion, which Kyiv denies.

The dramatic twist preceded an hour-long phone call between the Russian and US presidents, the second in recent days.

A White House spokesman described the conversation as 'positive'. 

Donald Trump later told reporters he was 'very angry' to hear about the alleged attack on the Valdai mansion in Novgorod province, which is favoured by Putin.

The US President said: 'It's one thing to be offensive. It's another thing to attack his house. 

'It's not the right time to do any of that. And I learned about it from President Putin today. I was very angry about it.'

After questions from reporters, he said it was 'possible' the attack did not happen. 

Last night, Ukrainian president Volodymyr Zelensky denied any attempt to kill his counterpart and accused Russia of a 'false flag' operation. 

Mr Zelensky said the claims were 'another round of lies' and a bid by a panicked Russia to undermine the peace talks.

According to Mr Lavrov, Russian defences destroyed 91 Ukrainian drones that targeted the mansion on Sunday night. He did not confirm whether Putin was there at the time.

Mr Lavrov accused Ukraine of 'state terrorism' and said Russia was already selecting targets for retaliatory strikes. 

Mr Lavrov also said in an interview published late on Monday that the West must understand that Russia holds the strategic initiative in Ukraine as discussions move forward.

The foreign minister, in a wide-ranging interview with state news agency RIA, also said Moscow was waiting for a reply ​from the United States to Russian President Vladimir Putin's proposal in September to extend for a ​year limits in a strategic arms pact.

Lavrov told RIA ​that Ukraine and Western countries had to come to terms with the fact that Russia held the initiative on the battlefield as the fourth anniversary of the Kremlin's 2022 invasion of its smaller ⁠neighbour approaches.

'Our principled position remains unchanged. The strategic initiative rests wholly with the Russian army and the West ​understands this,' Lavrov said.

Ukraine and Western countries, he ‍said, had to take account of the realities on the ground. Russia holds about ​19% of Ukrainian territory and has annexed four regions of the country as well as Crimea, seized in 2014.

Last night, Russian sources said Putin told Mr Trump the Kremlin was amending its negotiating position following the alleged drone attack.

Russian aide Yuri Ushakov said: 'Russia's position will be reviewed on a number of agreements reached at the previous stage and on the emerging interchanges.' 

Zelensky admitted last night that Ukraine cannot win its war against Russia without American support ​and that he does not trust ​Russian President ​Vladimir Putin.

'Can we win without American support? ⁠No,' Zelensky said in an interview on ​Fox News ‍show 'Special Report ​with Bret Baier' that aired on Monday, before laying out the difficulties that will be posed ‍by ‍a lack of US support.

'I don't trust Putin and he doesn't want success for Ukraine,' ⁠Zelensky said, adding his Sunday meeting with President Donald Trump ⁠was productive.