The latest talks could be an early litmus test on how seriously Moscow perceives President Trump's threats to impose sanctions — and how Russia might respond.
Russia has proposed another attempt at peace negotiations with Ukraine on Monday in Istanbul, but both sides remain firmly entrenched in positions likely to prolong the war.
Russia declared a three-day ceasefire in Ukraine starting May 8 for the anniversary of the Soviet Union's victory over Nazi Germany. Ukraine called for an immediate, 30-day truce instead.
The historic negotiations represent the first direct talks between the long-warring sides. However, leaders warn that reaching a peace deal could take time.