South Korea: North's nuke, missile threats won't work

South Korea's president said Saturday his country won't give in to North Korea's nuclear and missile threats, while Pyongyang accused Seoul of sending patrol boats into its territorial waters - the scene of past bloody naval clashes. In France, US President Barack Obama suggested a new, stronger response to North Korean nuclear and missile testing, saying the North has tested the limits of patient diplomacy intended to persuade the reclusive communist country to accept international demands and end to its nuclear program. The North's official Korean Central News Agency alleged the patrol boats were sailing into North Korean waters daily around the rivals' disputed western sea border. The Korean-language report warned that aggressors would be dealt "merciless punishment that will be beyond imagination." The claim was rejected by Seoul, which two days ago alleged one of the North's patrol boats violated its sea border in the same area. The boat turned back without incident after a 50-minute standoff with the South's naval ships, the South Korean military said.