Aqueous polishing slurries for chemical-mechanical polishing are effective for polishing copper at high polish rates. The aqueous slurries according to the present invention may include soluble salts of molybdenum dissolved in an oxidizing agent and molybdic acid dissolved in an oxidizing agent. Methods for polishing copper by chemical-mechanical planarization include polishing copper with low pressures using a polishing pad and a aqueous slurries including soluble salts of molybdenum dissolved in an oxidizing agent and molybdic acid dissolved in an oxidizing agent, particles of MoO.sub.3 dissolved in an oxidizing agent, and particles of MoO.sub.2 dissolved in an oxidizing agent.