They could start within a month if there is no ceasefire.
Trump told NBC News he was angry and "pissed off" when Russian President Vladimir Putin criticised the credibility of Ukrainian President Volodymyr Zelenskiy's leadership, NBC reported.
Trump flagged that he planned to speak with Putin this week.
During his 2024 presidential campaign, Trump promised repeatedly to end what he calls a "ridiculous" war in Ukraine, and he has focused heavily on the issue since taking office on January 20.
Trump himself has called for new elections in Ukraine and falsely called Zelenskiy a dictator.
Putin on Friday suggested Ukraine could be placed under a form of temporary administration to allow for new elections and the signature of key accords, which could effectively push out Zelenskiy.
"If Russia and I are unable to make a deal on stopping the bloodshed in Ukraine, and if I think it was Russia's fault ... I am going to put secondary tariffs on oil, on all oil coming out of Russia," Trump said.
"That would be, that if you buy oil from Russia, you can't do business in the United States," Trump said.
"There will be a 25 per cent tariff on all oil, a 25- to 50-point tariff on all oil."
He said the tariffs on Russian oil would come within a month without a ceasefire deal.
Trump said Putin knows he is angry with him, but said he had "a very good relationship with him" and "the anger dissipates quickly ... if he does the right thing."
Meanwhile, Finland's President Alexander Stubb said on Sunday he had told Trump that a deadline needs to be set for establishing a Ukraine ceasefire in order to make it happen.
"April 20 would be a good time for a full ceasefire without any conditions ... because a deadline is needed, because it is Easter and because President Donald Trump will have been in office for three months," Stubb told Finnish reporters in London.
Stubb on Saturday made a surprise trip to meet Trump in Florida, where they discussed strengthening their countries' bilateral partnership and also played a round of golf, Stubb's office said.
Earlier this week the United States announced separate agreements with Ukraine and Russia to pause their strikes in the Black Sea and against each other's energy targets.
Stubb told reporters Trump's patience with Russia was running out and the US had "far-reaching" plans if Russia will not accept a ceasefire.
