US President Donald Trump has vented anger at Russian President Vladimir Putin and threatened secondary tariffs of as much as 50 per cent on Russian oil if he feels Moscow is blocking his efforts to end the war in Ukraine.

They could start within a month if there is no ceasefire.

Trump told NBC News he was “p–sed off” when Putin criticised the credibility of Ukrainian President Volodymyr Zelensky’s leadership, NBC reported.

Ukraine’s leader, meanwhile, posted images of a week where he said most regions of his country had come under attack.

Trump also threatened “bombing” and “secondary tariffs” on Iran if the country did not come an an agreement with the US to ensure it did not develop a nuclear weapon.

Trump has flagged speaking to Putin this week.

During his 2024 presidential campaign, Trump promised repeatedly to end what he calls a “ridiculous” war in Ukraine. He has focused heavily on the issue since taking office on January 20.

Trump has called for new elections in Ukraine and falsely called Zelensky a dictator.

On Friday, Putin suggested Ukraine be placed under a form of temporary administration to allow for new elections and the signature of key accords, which could effectively push out Zelensky.

“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.

“There will be a 25 per cent tariff on all oil, a 25- to 50-point tariff on all oil.”

He said the oil tariffs would come within a month, unless there was a ceasefire deal.

Trump said Putin knew he was angry, 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 (British time) he had told Trump that a deadline was needed to establish a Ukraine ceasefire 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 said in London.

On Saturday, Stubb made a surprise trip to meet Trump in Florida. The pair discussed strengthening their countries’ bilateral partnership and also played a round of golf, Stubb’s office said.

Last week the US announced separate agreements with Ukraine and Russia to pause strikes in the Black Sea and against each other’s energy targets.

Stubb said Trump’s patience with Russia was running out and the US had “far-reaching” plans if Russia will not accept a ceasefire.

Iran responds to Trump letter

Iran has sent a response through Oman to Trump’s letter in which he urged Tehran to reach a nuclear deal, Iranian Foreign Minister Abbas Araqchi was cited as saying by the official IRNA news agency.

“Our policy is still to not engage in direct negotiations while under maximum pressure and military threats, however, as it was the case in the past, indirect negotiations can continue”, IRNA cited Araqchi as saying.

Earlier Kamal Kharrazi, an adviser to Iran’s supreme leader, said Tehran had not closed all doors to resolve its disputes with the US and was ready for indirect negotiations with Washington.

Tehran has so far rebuffed Trump’s warning to make a deal or face military consequences. Supreme Leader Ayatollah Ali Khamenei called the message deceptive and Araqchi said talks were impossible unless Washington changed its “maximum pressure” policy.

“The Islamic Republic has not closed all doors. It is ready for indirect negotiations with the United States in order to evaluate the other party, state its own conditions and make the appropriate decision,” Kharrazi said, according to state media.

“Our response includes a letter in which we detailed our views on the current situation and Trump’s letter”, Araqchi said.

In his first 2017-21 term, Trump withdrew the US from a 2015 deal between Iran and world powers that placed strict limits on Tehran’s disputed nuclear activities in exchange for sanctions relief.

After Trump pulled out in 2018 and reimposed sweeping US sanctions, the Islamic Republic breached and has since far surpassed those limits in its escalating program of uranium enrichment.

Western powers accuse Iran of having an clandestine agenda to develop nuclear weapons capability by enriching uranium to a high level of fissile purity, above what they say is justifiable for a civilian atomic energy program.

Tehran says its nuclear program is for civilian energy purposes.

-with AAP