Jim Mattis will deliver a “medium-tough” message to China this week about its military expansionism during the defence secretary’s first visit to the country, even as the Trump administration seeks Beijing’s help to denuclearise North Korea and tensions flare over trade.

Mr Mattis will prioritise future talks with North Korea despite his concerns over China’s militarisation in the South China Sea, according to a senior Pentagon official with knowledge of the three-day visit that is the first by a US defence secretary since 2014.

The Trump administration has identified China as a “ strategic competitor” and defence officials are preoccupied by Beijing’s rapid expansion of military capabilities. Earlier this month, Mr Mattis accused the country of “ intimidation and coercion” by placing weapons, including bombers on a string of disputed islands in the South China Sea.