Washington DC - US President Donald Trump told Russia on Monday to end its Ukraine war within 50 days or face massive new economic sanctions as he laid out plans for new infusions of weaponry for Kyiv via NATO.

Trump said he was "very, very unhappy" with Vladimir Putin, underlining his insistence that his patience had finally snapped with the Russian leader's refusal to end his three-year-old invasion of Ukraine.

"We're going to be doing very severe tariffs if we don't have a deal in 50 days, tariffs at about 100 percent," Trump said during an Oval Office meeting with NATO Secretary General Mark Rutte.

The 79-year-old added that they would be "secondary tariffs" that target Russia's remaining trade partners – thereby seeking to cripple Moscow's ability to survive already sweeping Western sanctions.

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Trump and Rutte also unveiled a deal under which the NATO military alliance would buy arms from the US – including Patriot anti-missile batteries – and then send them to Ukraine to help it battle Russia's invasion.

"This is billions of dollars' worth of military equipment that is going to be purchased from the United States, going to NATO... and that's going to be quickly distributed to the battlefield," Trump said.

Rutte said Ukraine would get "massive numbers" of weapons under the deal, which is aimed at placating Trump's long-held complaints that the US is paying too much to aid Ukraine.

However, EU foreign policy chief Kaja Kallas said Trump's deadline, while "very positive," was too far into the future.

"Fifty days is a very long time if we see that they are killing innocent civilians every day," Kallas said.