US President Donald Trump has announced the US will send "top-of-the-line weapons" to Ukraine via Nato countries, while also threatening Russia with severe tariffs if a deal to end the war is not reached within 50 days.

"We want to make sure Ukraine can do what it wants to do," Trump said following a meeting with NATO chief Mark Rutte in Washington.

Rutte confirmed the US had decided to "massively supply Ukraine with what is necessary through NATO" and that the Europeans would foot the bill.

European countries will send Kyiv their own Patriot air defence systems, which Ukraine relies on to repel Russia's deadly air strikes, and replacements will then be issued by the US, Trump said.

Neither Rutte nor Trump elaborated on the weaponry that will be sent to Kyiv, but Rutte said the deal included "missiles and ammunition".

However, the president did say "top-of-the-line-weapons" worth billions of dollars would be "quickly distributed to the battlefield" in order to support Ukraine.

"If I were Vladimir Putin today... I would reconsider whether I should not take negotiations about Ukraine more seriously," Rutte said, as Trump nodded.

Ukrainian President Volodymyr Zelensky said on X that he spoke with Trump after his meeting with Rutte, and thanked him for his "willingness to support Ukraine and to continue working together to stop the killings and establish a lasting and just peace".

"We discussed the necessary means and solutions with the President to provide better protection for people from Russian attacks and to strengthen our positions. We are ready to work as productively as possible to achieve peace," he said.

On the tariffs front, Trump said that the US would impose 100% secondary tariffs targeting Russia's remaining trade partners if a peace deal with Ukraine was not reached within 50 days.

This would see any country that trades with Russia face a tax if they want to sell their products to the US.

For example, if India keeps buying oil from Russia, US companies that purchase Indian goods would have to pay a 100% import tax, or tariff, when the products reach American shores.

This would make the goods so expensive that US businesses would likely choose to buy them cheaper from elsewhere, resulting in lost revenue for India.

The intention is also to hobble Russia's economy. Theoretically, if Moscow were unable to generate money by selling oil to other nations, it would also have less money to finance its war in Ukraine.

Given that oil and gas account for almost a third of Moscow's state revenue and more than 60% of its exports, 100% tariffs could make something of a dent in Russia's finances.

Still, the Moscow Stock Exchange Index rose sharply following the announcement, likely as investors were expecting Trump, who last week teased a "major statement" on Russia, to pledge even harsher measures.

Although details about both the tariffs and the Nato weapons deal was scant, Monday was the first time Trump pledged new military equipment for Ukraine since returning to the White House.

The briefing was also notable for the tone struck by the US president, whose rhetoric on Vladimir Putin has become increasingly harsh.

Not for the first time, Trump implied Kyiv bore some responsibility for Russia's decision to launch its full-scale invasion of Ukraine in February 2022.

But he mostly appeared frustrated at the lack of progress in ending a conflict which he once seemed to believe could be easily solvable.

Asked about his relationship with Putin, Trump said that the two speak "a lot about getting this thing done" but voiced his displeasure at the fact that "very nice phone calls" with the Russian president are often followed by devastating air strikes on Ukraine, which have been growing in intensity and frequency.

"After that happens three or four times, you say: the talk doesn't mean anything," Trump said.

"I don't want to call him an assassin, but he's a tough guy. It's been proven over the years, he fooled a lot of people – Clinton, Bush, Obama, Biden," he added. "He didn't fool me. At a certain point, talk doesn't talk, it's got to be action."

Two rounds of ceasefire talks between Russia and Ukraine took place earlier this year, but no other meetings have so far been scheduled - something Moscow has blamed on Kyiv.

Ukraine's President Zelensky is currently hosting US envoy Keith Kellogg in Kyiv and earlier on Monday hailed a "productive meeting" - saying he was "grateful" to Trump for his support.

The Kremlin did not immediately comment on the announcement, but commentary trickling in from Moscow appeared to indicate a measure of relief.

Pro-Kremlin pundit and former Putin aide Sergei Markov called the tariffs announcement "a bluff" that indicated Trump had "given up on trying to achieve peace in Ukraine".

Senator Konstantin Kosachev argued that "if this is all Trump had to say about Ukraine today, then so far it's been much ado about nothing".

In 50 days, a lot could change "both on the battlefield and in the minds of the powers that be in the US and NATO," Kosachev wrote.

Trump's decision led to praise from critics, including from within the rival Democratic Party.

The decision to send Patriot missiles to Ukraine, "made possible through the meaningful investments of our European partners, will save countless Ukrainian lives from Putin's horrific assault," said Democratic Senator Jeanne Shaheen, the top Democrat on the powerful Senate Foreign Relations Committee.

She called the measure "positive, but overdue" and said that the US needs to provide "a sustained flow of security assistance to Ukraine over the long term" in order to convince Putin to end the war.

Denys Podilchuk, a 39-year-old Ukrainian dentist from Kyiv, praised European leaders for helping to persuade Trump.

"I am pleased that finally European politicians, with their patience and convictions, have slightly swayed him (Trump) to our side, because from the very beginning it was clear that he did not really want to help us," he told Reuters.