KIEV, Ukraine (AP) — Ukrainian President Petro Poroshenko said he was abandoning a unilateral cease-fire in the conflict with pro-Russian separatists and sending military forces back on the offensive after talks with Russia and European leaders failed to start a broader peace process.

Poroshenko’s decision, announced shortly after the much-violated 10-day cease-fire expired, raises the prospect of renewed escalation of a conflict that has killed more than 400 people.