Trump arms Ukraine and threatens sanctions on countries that buy Russian oil

US President Donald Trump announced new weapons for Ukraine on Monday, and threatened sanctions on buyers of Russian exports unless Russia agrees a peace deal, a major policy shift brought on by frustration with Moscow's ongoing attacks on its neighbour.

But Trump's threat of sanctions came with a 50-day grace period, a move that was welcomed by investors in Russia where the rouble recovered from earlier losses and stock markets rose.

Sitting with NATO Secretary General Mark Rutte in the Oval Office, Trump told reporters he was disappointed in Russian President Vladimir Putin and that billions of dollars of US weapons would go to Ukraine. "We're going to make top-of-the-line weapons, and they'll be sent to NATO," Trump said, adding that Washington's NATO allies would pay for them.

The weapons would include Patriot air defence missiles Ukraine has urgently sought, he said.

"It's a full complement with the batteries," Trump said. "We're going to have some come very soon, within days."

"We have one country that has 17 Patriots getting ready to be shipped... we're going to work a deal where the 17 will go or a big portion of the 17 will go to the war site."

Rutte said Germany, Finland, Denmark, Sweden, Norway, the United Kingdom, the Netherlands and Canada all wanted to be a part of rearming Ukraine.

Trump's threat to impose so-called secondary sanctions on Russia, if carried out, would be a major shift in Western sanctions policy. Lawmakers from both US political parties are pushing for a bill that would authorise such measures, targeting other countries that buy Russian oil.

Throughout the more than three-year-old war, Western countries have cut most of their own financial ties to Moscow, but have held back from taking steps that would restrict Russia from selling its oil elsewhere. That has allowed Moscow to continue earning hundreds of billions of dollars from shipping oil to buyers such as China and India.

"We're going to be doing secondary tariffs," Trump said. "If we don't have a deal in 50 days, it's very simple, and they'll be at 100 per cent."

A White House official said Trump was referring to 100 per cent tariffs on Russian goods as well as secondary sanctions on other countries that buy its exports. Eighty-five of the 100 US senators are co-sponsoring a bill that would give Trump the authority to impose 500 per cent tariffs on any country that helps Russia, but the chamber's Republican leaders have been waiting for Trump to give them the go-ahead for a vote.

Ukrainian President Volodymyr Zelenskyy said on Telegram he had spoken to Trump and "thanked him for his readiness to support Ukraine and to continue working together to stop the killings and establish a lasting and just peace".

Zelenskyy held talks with Trump's envoy Keith Kellogg on Monday.

In Kyiv, people welcomed Trump's announcement but some were cautious about his intentions.