Ukraine-U.S. ceasefire talks took 7 hours. The hard part will be getting Russia to agree.

All eyes were on Moscow on Wednesday after American and Ukrainian officials said they would be willing to enforce a 30-day ceasefire in the country's three-year war — and made it clear the ball was in Russia’s court. Russian President Vladimir Putin is yet to respond to the proposal hashed out by Secretary of State Marco Rubio and his Ukrainian counterparts in Saudi Arabia on Tuesday. But some Russian officials and hardline commentators have poured cold water on a plan that, in theory at least, would halt its advances on the battlefield. Russia’s position would not be determined “abroad due...