On September 10, Trump sacked the national security adviser John Bolton as he strongly disagreed with John Bolton's suggestion about applying Libyan model to North Korea nuclear deal and mentioning Muammar Gaddafi. However, Bolton himself claims he was not sacked but resigned. Donald Trump selected hostage negotiator of DPRK Robert O'Brien as the new U.S. national security adviser. Some of Senate Republicans including Lindsey Graham praised Mr Trump's pick and mentioned, He's got great negotiating skills, and "he would be a very sound policy adviser." North Korea envoy Stephen Biegun confirmed as deputy secretary of state as Pompeo's number two. While Pompeo was recognized as a protector of Trump, Biegun is unknown for his partisanship. From Dec 15 to 21, Biegun visited South Korea, Japan and China as nuclear tensions climb with North Korea.