A Japanese government-funded study published Friday is warning that China is becoming less afraid of angering its neighbors as it pursues a bolder maritime policy.
The annual report by the National Institute for Defense Studies said China's rising national strength and enhanced military capabilities are helping drive Beijing's rising assertiveness.
China-Japan relations have suffered since September when Tokyo nationalized a group of East China Sea islands that have been the focus of a decades-long dispute.
Beijing responded angrily. It began sending regular government ships to patrol the Japanese-controlled islands, in what observers say is an effort to establish de facto control of the area.
The Japanese report Friday said signs of Chinese aggression were evident before the island purchase. It said China's actions "clearly reveal it was meticulously preparing measures for advancing its claim over the islands from a very early stage."
Ralph Cossa, president of the Hawaii-based Pacific Forum, says the Japanese report is an attempt to "throw the ball back in China's court."
"The Chinese have said the problem was the nationalization of those islands, that this changed the status quo, and that it is all Japan's fault," said Cossa. "So the Japanese are trying to point out that the Chinese were already preparing to do this, they were already flexing their muscles in the South China Sea and they were already doing other things."
Cossa says there is a degree of truth to the argument of both sides. But he says the report will not likely change Japan's foreign policy since it is already well aware of what it is dealing with in China.
He says China may continue to "annoy" and "bully" the Japanese over the island issue, but he does not foresee a wider conflict between the two Asian powers.
"The real question is now that [Chinese President] Xi Jinping has fully come to power, will he want to defuse some of this or will he want to continue to ratchet it up?" asked Cossa. "We've seen some signals in both directions, so I think it's a little too soon to tell."
Observers are also watching Japan's new leader, Prime Minister Shinzo Abe, who is known for his nationalistic views and has taken a firm stance on the island issue since coming to power.