SEOUL, April 19 (Yonhap) -- President Lee Myung-bak pledged Monday to take "resolute" measures against those responsible for the sinking of a South Korean naval ship last month as he consoled the nation over one the country's worst naval disasters. "As the president, I will ascertain the cause of the Cheonan's sinking to the last detail," he said in his address broadcast live. "I will deal resolutely with the results and make sure such an incident does not recur."