The General made the comment during an appearance before the Senate Armed Service Committee. He claimed Chinese technology is advancing rapidly whilst the country learns military tactics from the West. Beijing has an ambitious plan to develop a more advanced military than the US by 2049.
General Milley said: “I think China is the main challenger to US national security for the next 50, 100 years.
“I think some historian in 2119 will look back at this century, write a book, and the central theme of the story will be the relationship between the United States and China.”
China and the US have clashed over a number of issues in recent years.
These include sovereignty of the South China Sea and Taiwan as well as the programme of sanctions implemented after Donald Trump became President.
READ MORE: South China Sea – How Beijing breached 2015 pledge
General Milley warned that China is dramatically improving its military capability.
He commented: “China is improving their military very, very rapidly in space, air, cyber, maritime and land domains.
“They’re outspending us in research, development and procurement.
“We, the United States, need to make sure that we do not lose our advantages that we have relative to other countries, specifically relative to China.”
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The US, and other Western powers including Britain, have been sending warships on ‘freedom of navigation’ patrols through the South China Sea.
These are intended to dispute Beijing’s exclusive claim to control the territory, which is also partly claimed by a number of other regional powers.
General Milley added China had learned extensively from observing the US in recent conflicts.
He said: “They watched us very closely in the First Gulf War, Second Gulf War, watched our capabilities, and in many, many ways they have mimicked those.”