Trump arms vow diminishes hope of Ukraine peace: Russia

US President Donald Trump's decision to ramp up arms shipments to Ukraine is a signal to Kyiv to abandon peace efforts, Russia says, vowing it would not accept the "blackmail" of Washington's new sanctions ultimatum.

Trump announced a toughened stance on Russia's war in Ukraine on Monday, setting a 50-day deadline for Moscow to reach a ceasefire or face sanctions. The US also promised more missiles and other weaponry for Kyiv.

Maria Zakharova, a spokeswoman for the Russian Foreign Ministry, condemned the move.

"It is obvious that the Kyiv regime consistently perceives such decisions by the collective West as a signal to continue the slaughter and abandon the peace process," Zakharova told a news briefing in Moscow.

Russia's all-out war against Ukraine in February, 2022, has led to Europe's bloodiest conflict since World War Two, with the United States estimating that 1.2 million people have been injured or killed.

Moscow says it was forced to launch the war to protect itself from an expanding NATO. Ukraine and most Western governments call Russia's war a colonial-style land grab.

Russian forces now control around one fifth of Ukrainian territory and are slowly but steadily advancing across a vast frontline, sustaining what the US believes are heavy losses along the way.

Trump, who has made ending the conflict a priority of his administration, is threatening "100 per cent tariffs on Russia" and secondary sanctions on countries that buy Russian oil if Moscow does not agree to a ceasefire deal by his 50-day deadline.

"An unprecedented number of sanctions and restrictions have been imposed on our country and our international partners. There are so many of them that we view the threat of new sanctions as mundane," Zakharova said.

"The language of ultimatums, blackmail, and threats is unacceptable to us. We will take all necessary steps to ensure the security and protect the interests of our country."

Both Russia's President Vladimir Putin and Trump have repeatedly cautioned over the escalatory risks of the conflict, which they cast as a proxy war between the world's two biggest nuclear powers.

US efforts to broker peace negotiations between Kyiv and Moscow, however, have faced repeated setbacks.

Russia says it is ready to hold further talks, but has made it clear it wants all of the territory of four Ukrainian regions it has claimed as its own - terms which Ukraine say are unacceptable and would amount to a capitulation.

Moscow is also keen to revive its battered bilateral relationship with the United States if possible, though Trump's latest moves on Ukraine have soured the atmosphere.

Trump said on Monday that he was "very unhappy" and "disappointed" with Putin and cast his decision to send more arms to Ukraine as intended to jolt Russia towards peace.

Reuters reported on Tuesday that Putin intends to keep fighting in Ukraine until the West engages on his terms for peace, unfazed by threats of tougher sanctions, and that his territorial demands may widen as Russian forces advance.

Earlier on Thursday, former Russian President Dmitry Medvedev said that Russia had no plans to attack NATO or Europe. But he said it should respond and, if necessary, launch pre-emptive strikes if it believed the West was escalating what he cast as its full-scale war against Russia.

"We need to act accordingly. To respond in full. And if necessary, launch preemptive strikes," Medvedev was quoted as saying.

The remarks by Medvedev, reported in full by the TASS state news agency, indicate that Moscow sees the confrontation with the West over Ukraine escalating after Trump's latest decisions.

"What is happening today is a proxy war, but in essence it is a full-scale war (launches of Western missiles, satellite intelligence, etc.), sanctions packages, loud statements about the militarisation of Europe," Medvedev said, according to TASS.