US Secretary of State Rex Tillerson is reportedly considering replacing his top Asia diplomat with a former US Treasury Department official who has little experience in diplomacy and regional security matters as the North Korea nuclear missile crisis grows more serious. The change comes amid new estimates that Pyongyang will be able to field a reliable, nuclear-tipped intercontinental ballistic missile capable of reaching North America as early as next year. Olin Wethington, a former US Treasury Department official and a non-resident fellow at the Atlantic Council, is now Tillerson’s favourite candidate to replace veteran diplomat Susan Thornton, the current acting assistant secretary of state for East Asian and Pacific Affairs, BuzzFeed News reported on Monday. “Wethington has been looked at for the job, but I do not believe a formal internal decision has been made to offer it to him yet,” said Douglas Paal, vice president for studies at the Carnegie Endowment for International Peace. Paal said Wethington may or may not get the job. Thornton will likely move on to an appropriately rewarding position, he said. Although he has a deep background in doing business in China and specialising in investment and finance related to US government agencies, Wethington possesses little experience in diplomacy and regional security issues. US warns Chinese firms with ties to North Korea may still face sanctions Previously, Wethington served as assistant secretary for international affairs at the US Treasury, and was responsible for insurer American International Group’s expansion into China, according to his resume on the Atlantic Council website. Scott Kennedy, an Asia expert at the Centre for Strategic and International Studies, told BuzzFeed that Wethington would have a steep learning curve on security and political issues, if nominated. Kennedy said it is risky to appoint an assistant secretary who lacks deep knowledge and experience on issues of language and diplomacy related to highly sensitive issues such as Taiwan, the South China Sea and North Korea. A State Department spokeswoman declined to give details regarding the reported replacement, referring to it as a matter of “possible presidential nominations” that would be handled by the White House. On that note, the US Defence Department’s new assessment raised the urgency to rein in North Korean nuclear weapon programme. Pyongyang will be able to field a reliable, nuclear-capable ICBM as early as next year, when it could strike North American cities with atomic weapons, the Washington Post reported on Tuesday. Trump underlines his bulldozer diplomacy by choosing Tillerson as US secretary of state Thornton has been at the position for about six months since US President Trump took office. BuzzFeed said Thornton was Tillerson’s first choice, but the White House opposed her appointment due to concerns that her views were out of step with the president’s agenda – a claim State Department officials deny. Thornton appeared in front of a US Senate Foreign Affairs Committee hearing on Tuesday, the first Trump administration official testifying on the North Korea issue publicly. Thornton said US new sanctions against North Korea could be coming “soon”. Uncertainty in Asia over Trump’s top diplomat pick Kennedy suggested that Thornton’s approach may not be tough enough to satisfy the White House. “She believes in extensive diplomacy and long-term approaches and integration in the global system as an approach toward China,” Kennedy said. Thornton speaks Mandarin Chinese.