I STANBUL—President Trump’s ultimatum for Russian President Vladimir Putin is showing no signs of bringing Russia and Ukraine any closer to peace. The third round of direct talks between Ukrainian and Russian officials, held Wednesday in Istanbul, yielded few results. The two sides met for less than an hour.

Russian and Ukrainian delegates have begun their third set of direct talks in Istanbul, days after US President Donald Trump gave Moscow a 50-day deadline to make peace or face “very severe tariffs.”

During the talks, Ukraine proposed holding a summit between President Volodymyr Zelensky and Russian President Vladimir Putin before the end of August, according to National Security and Defense Council Secretary Rustem Umerov,