Korea watchers want to know, as the American leader spends an hour and a half on the phone with the Chinese party boss, Xi Jinping.

The new South Korean administration will likely make efforts to buy time for U.S. trade talks, as it studies the negotiations of bigger neighbours Japan and China for leverage, according to sources familiar with the ruling party's thinking.

The new South Korean president, Lee Jae-myung, calls himself a foreign policy “pragmatist”. He says he is driven by South Korea’s national interest, rather than ideology, and has spoken of his desire to improve relations with China and North Korea.