SEOUL: South Korean investigators sought an extension of a warrant to arrest impeached President Yoon Suk Yeol, as visiting US Secretary of State Antony Blinken reaffirmed confidence in the key Asian ally's handling of the political turmoil. Investigators probing Yoon over his Dec 3 martial law proclamation failed to serve an arrest warrant on Friday, blocked by presidential security service guards who formed a human chain to prevent access to Yoon. The arrest warrant, the first for a sitting