A new defense secretary who was more in line with Mr. Trump's thinking could be an opportunity for China, said Wu Xinbo, Director of the Center for American Studies at Fudan University.

Under Mr. Mattis, the Pentagon appeared to act "separately from the Trump team in dealing with China," Mr. Wu said. Now that could change.

"Certainly Trump wants a more compliant secretary of defense," said Mr. Wu. "With China Trump, focuses on the economy, not security or geopolitics. But the military has been pushing vigorously on Taiwan and the South China Sea. Let’s see if this will change."