WASHINGTON -- US President Donald Trump said Monday that the United States will send weapons to Ukraine through NATO, and threatened "severe tariffs" targeting Russia if a ceasefire deal is not reached in 50 days.

Trump announced an agreement with NATO regarding weapons to assist Ukraine while meeting NATO Secretary General Mark Rutte in the Oval Office.

"We are going to be sending them weapons and they're going to be paying for them," said Trump, adding that the United States will manufacture those weapons.

"We're going to be doing very severe tariffs if we don't have a deal in 50 days," Trump said of Russia.

Trump noted there would be "secondary tariffs" of about 100 percent, multiple news outlets reported.

US Commerce Secretary Howard Lutnick clarified later that Trump meant "economic sanction" when he threatened "secondary tariffs" against Russia if it did not reach a deal to end the war in Ukraine within 50 days, The Washington Times reported.

Speaking to reporters after the Oval Office meeting, Trump said that the deal with the NATO allies was done and fully approved, The New York Times reported.

"We'll send them a lot of weapons of all kinds," Trump said. "And they're going to deliver those weapons immediately to the site, to the site of the war, different sites of the war, and they're going to pay for 100 percent of them."

Trump also told reporters that some Patriot systems will arrive in Ukraine within days, according to ABC News.

Trump said European countries that have Patriots will transfer them to Ukraine and "they're going to start arriving very soon," ABC News added.