Chinese Foreign Ministry spokesman Lu Kang on Saturday called on the US to avoid discussion of the issue and reasserted China's claim of sovereignty over the tiny uninhabited islands, known in Japanese as the Senkaku and Chinese as Diaoyu.
The 1960 US-Japan treaty is "a product of the Cold War, which should not impair China's territorial sovereignty and legitimate rights", Lu was quoted as saying in a statement posted on the ministry's website.
"We urge the US side to take a responsible attitude, stop making wrong remarks on the issue involving the Diaoyu islands' sovereignty, and avoid making the issue more complicated and bringing instability to the regional situation," Lu said.
On his first trip to Asia as secretary of defence, Mattis explicitly stated in Tokyo that the Trump administration will stick to the previous US stance that the US-Japan security treaty applies to defending Japan's continued administration of the Senkaku islands.
The islands that lie between Taiwan and Okinawa were under US administration from the end of World War II until their return to Japan in 1972. China cites historical records for its claim, and Japan's move to nationalise several of the islands in 2012 set off anti-Japanese riots in China and prompted the government to dispatch ships and planes to the area around them as a challenge to Japanese control.
Chinese officials and scholars say they anticipate further turbulence in relations with the US under Trump.