US President Donald Trump warned on Monday that he will slap “very severe” 100% tariffs on Russian imports unless Moscow agrees to a ceasefire deal in Ukraine within 50 days. The ultimatum, delivered during an Oval Office meeting with NATO Secretary-General-designate Mark Rutte, represents Trump’s most sweeping trade threat against Russia since taking office. Trump said the measures would include “secondary tariffs” penalising companies and countries that continue to trade with Russia, a move aimed at severing remaining financial lifelines to the Kremlin. “We’re going to be doing very severe tariffs if we don’t have a deal,” he told reporters, adding that he views trade tools as effective leverage for ending conflicts. Alongside the tariff threat, Trump announced plans to step up military assistance to Kyiv. The United States will manufacture additional Patriot air-defence systems and other weapons for Ukraine, he said, while European allies will cover the cost through coordinated purchases organised by NATO. The pledge follows a surge in Russian missile and drone strikes that Ukrainian officials say has killed dozens of civilians in recent weeks. Kremlin spokesman Dmitry Peskov said Moscow would analyse the US remarks, while other Russian officials dismissed the move as an “ultimatum”. Financial markets in Russia appeared unperturbed: the MOEX index rose about 2.7% on Monday and the rouble recovered early losses against the dollar. Whether the tariff threat shifts President Vladimir Putin’s calculus on Ukraine now hinges on the next 50 days.