President Donald Trump says the United States will supply weapons to Ukraine via NATO and will he would make a "major statement" on Russia next week.
In recent days, Trump has expressed frustration with Russian President Vladimir Putin over the lack of progress towards ending the war sparked by Russia's full-scale invasion of Ukraine in February 2022.
"I think I'll have a major statement to make on Russia on Monday," Trump told NBC News on Thursday, declining to elaborate.
Trump also told NBC News about what he called a new deal between the US, NATO allies and Ukraine over weapons shipment from the United States.
"We're sending weapons to NATO, and NATO is paying for those weapons, 100 per cent. So what we're doing is the weapons that are going out are going to NATO, and then NATO is going to be giving those weapons (to Ukraine), and NATO is paying for those weapons," Trump said.
"We send weapons to NATO, and NATO is going to reimburse the full cost of those weapons."
For the first time since returning to office, Trump will send weapons to Kyiv under a presidential power frequently used by his predecessor, two sources familiar with the decision said on Thursday.
Trump's team will identify arms from US stockpiles to send to Ukraine under the Presidential Drawdown Authority, which allows the president to draw from weapons stocks to help allies in an emergency, the sources said, with one saying they could be worth around $US300 million ($A457 million).
Trump on Tuesday said the US would send more weapons to Ukraine to help the country defend itself against intensifying Russian advances.
The package could include defensive Patriot missiles and offensive medium-range rockets, but a decision on the exact equipment has not been made, the sources said. One of the people said this would happen at a meeting on Thursday.
The Trump administration has so far only sent weapons authorised by former president Joe Biden, who was a staunch supporter of Kyiv. The Pentagon and the White House did not immediately respond to a request for comment.
Trump had pledged to swiftly end the war but months into his presidency, little progress has been made. The Republican president has sometimes criticised US spending on Ukraine's defence, spoken favourably of Russia and publicly clashed with Ukraine's leader. However, sometimes he has also voiced support for Kyiv and expressed disappointment in the leadership of Russia.
Russia unleashed heavy airstrikes on Ukraine on Thursday before a conference in Rome at which Kyiv won billions of dollars in aid pledges, and US-Russian talks at which Washington voiced frustration with Moscow over the war.
Addressing the Rome conference on Ukraine's reconstruction after more than three years of war, Ukraine President Volodymyr Zelenskiy urged allies to "more actively" use Russian assets for rebuilding and called for weapons, joint defence production and investment.
Participants pledged over 10 billion euros ($A18 billion) to help rebuild Ukraine, Italian Prime Minister Giorgia Meloni said. The European Commission, the EU's executive, announced 2.3 billion euros ($A4.1 billion) in support.
At talks with Russian Foreign Minister Sergei Lavrov while in Malaysia, US Secretary of State Marco Rubio said he had reinforced the message that Moscow should show more flexibility.
"We need to see a roadmap moving forward about how this conflict can conclude," Rubio said, adding that the Trump administration had been engaging with the US Senate on what new sanctions on Russia might look like.
"It was a frank conversation. It was an important one," Rubio said after the 50-minute talks in Kuala Lumpur. Moscow's foreign ministry said they had shared "a substantive and frank exchange of views".
Zelenskiy said Thursday's assault by Russia had involved around 400 drones and 18 missiles, primarily targeting the capital.
with AP