China's new ambassador to the US has warned Washington not to "drop a stone on its feet" by meddling in a territorial dispute between Beijing and Tokyo.
In his first direct remarks on the territorial dispute since his appointment last month, Cui Tiankai also said China was alert to a "negative trend" of right-wing intentions in Japanese politics, and denounced Japanese Prime Minister Shinzo Abe's wearing of a camouflage uniform at a weekend exhibition as a political stunt.
Analysts said the tough rhetoric was in line with the new Chinese leadership's increasing assertiveness in diplomatic affairs.
US Defence Secretary Chuck Hagel said on Monday that the disputed Diaoyu Islands, known as the Senkakus in Japan, were under Japanese administration and fell under a US-Japanese security treaty.
Cui said the United States should bear in mind that it was Japan that was creating tensions and warned that any mis-step by Washington could see it "suffer a big loss for little gain".
"We don't want other countries to pick up the stone made by Japan and drop it on their feet," Cui said. "Other countries should not cause long-term consequences just because of their short-term needs."
Sino-Japanese ties have become troubled since September, when the Japanese government bought three of the five uninhabited islands from private owners.
Last week, Beijing denounced a visit by Japanese lawmakers and officials to Tokyo's controversial Yasukuni shrine, which glorifies Japan's wartime past.
Abe said his ministers "will not yield to any kind of intimidation" on their visits to the shrine. On Saturday, he wore a camouflage jacket and helmet while getting into a Japanese Ground Defence Force tank at a publicity event sponsored by a video-sharing website.
"What kind of show is this?" Cui said. "I believe such actions are contrary to the common wishes and interests of the international community."
He said Japan's invasion of China before the second world war had been an act of aggression and an "inhuman crime".
Lin Xiaoguang , an international relations specialist at the Central Party School, said Cui's remarks indicated Beijing was contemplating action should Japan and the US get closer.
"Cui is sending a warning to the US that Washington may get short-term gains if it contains China with Japan, but eventually it will lose," he said. "China is telling the US that it will not just sit and do nothing."
President Xi Jinping called Japan's purchase of the islands a "farce" in September, when he was vice-president.
China called off an annual financial meeting with Japanese and South Korean officials that was due to be held in New Delhi this week.
Meanwhile, the vice-president of Japan's Liberal Democratic Party, Masahiko Komura, cancelled a trip to China due to difficulties in arranging a meeting with Xi.