SEOUL, South Korea — Looking to take a harder line after North Korea’s recent nuclear test and rocket launch, Seoul and Washington will begin talks as early as next week on deploying a sophisticated U.S. missile defense system in South Korea, officials said Friday. The new tough stance follows South Korea’s decision to shut down an inter-Korean factory park that had been the rival Koreas’ last major symbol of cooperation, but that Seoul said had been used by North Korea to fund its nuclear and missile programs.