US President Donald Trumpon Thursday declared China the "grand champions" of currency manipulation, indicating he has not "held back" in his previous assessment. His statement, made during an interview with Reuters, came hours after his new Treasury Secretary Stephen Mnuchin pledged a more methodical approach to analyze Beijing's foreign exchange practices.

Trump also told Reuters that China could solve the national security challenge posed by North Korea "very easily if they want to."

The impression Trump left was that he has been talking about China based on his own imagination. He knows nothing about China's currency policies and had no idea about the nature of Sino-North Korean relations.

What he saw was a Chinese trade surplus and that many Chinese goods are sold at cheaper prices than US products. He felt that the yuan was "kept low artificially" because 1 yuan is worth a lot less than 1 dollar. This perception is obviously fictitious. China sold a lot of its foreign currency reserves last year to maintain yuan stability. Trump's accusation of China's forex policy is groundless.

As for Sino-North Korean relations, many Americans, Trump included, believe Pyongyang would listen to whatever Beijing says. But the latest critique from Pyongyang's official news agency, which lashed out at Beijing, clearly suggests otherwise.

Trump's comments indicate that he has not discussed the currency manipulation issue with Mnuchin. China's current currency policy, which aims at preventing yuan depreciation, is actually in line with Trump's wish.

As US president, Trump should be more cautious when commenting on other countries. After all, the White House is not a standup comedy theater. Every word of the US president will be recorded and discussed. When the US president says whatever comes across his mind and is not held responsible for his words, people do not know how to respond to it.

Many countries have been criticized by Trump but it is still unclear what these criticisms stand for in diplomatic terms.

China is earnest about maintaining sound Sino-US relations and takes the US' opinions seriously. However, China won't be able to satisfy unreasonable demands and if the US insists on doing so, frictions are bound to emerge.

Trump has demonstrated extraordinary capabilities in his past successful career. However he should start a new learning process when entering an arena such as the Sino-US diplomacy. We strongly feel that his knowledge about China is ill-matched for his responsibility. Given the gravity of Sino-US ties, we hope it could be remedied as soon as possible in the US institutions.