Russia's Vladimir Putin has rejected President Trump's ultimatum for Moscow to sign a ceasefire deal with Ukraine in the next 50 days. Trump has threatened to issue a 100% tariff on any country that does business with Russia if no ceasefire deal is reached.

Russian weapons pounded four Ukrainian cities overnight from Tuesday to Wednesday, injuring at least 15 people in an attack that mostly targeted energy infrastructure, officials said.

But using heavy tariffs to stop countries buying Russian oil would be a blunt tool – and while they could significantly squeeze Russia’s war funding, they could also unleash more havoc on the rest of...