WASHINGTON (AP) — In a symbolic show of support for Ukraine's fledgling government, President Barack Obama is meeting with Ukrainian President Petro Poroshenko in the Oval Office on Thursday after the leader of the former Soviet republic speaks to a rare joint session of Congress. The U.S. and Western allies have condemned Russia's provocations, levying a series of economic sanctions and restricting President Vladimir Putin's involvement in some international organizations. On Wednesday, shelling in rebel-held parts of the east killed at least 12 civilians, as a top leader of pro-Russian rebels rejected Ukrainian legislation meant to end the unrest by granting self-rule to large swaths of the east.