Japan might disclose evidence to bolster its claim that a Chinese frigate locked its weapon-targeting radar on a Japanese ship, after China rejected the charge, officials say.
The incident, which Japan said happened last week, marked the first time the two nations' navies have locked horns in a territorial dispute that has some commentators warning about possible armed conflict.
The neighbours, also the world's second and third-largest economies, have seen ties sour over uninhabited Japanese-controlled islands in the East China Sea known as Senkaku in Tokyo and Diaoyu by Beijing, which claims them.
"The government is considering the extent of what can be disclosed," Itsunori Onodera, Japan's defence minister, said on a television programme on Saturday.
Onodera also proposed setting up a military hotline between the two countries, "so that we would be able to communicate swiftly when this kind of incident happens."
His comments came a day after Shinzo Abe, prime minister, demanded that China apologise and admit the incident had happened.
Japan also charges that a Chinese frigate's radar locked onto a helicopter last month, a procedure known as "painting" which is a precursor to firing modern weaponry.
On both January 19 and January 30, China's defence ministry said in a statement sent to the AFP news agency the Chinese ship-board radar maintained normal operations and "fire-control radar was not used".
Japan hit back, with Fumio Kishida, foreign minister, saying he "cannot accept" the explanation and Abe demanding an apology from China.
Abe described on Thursday the radar incident as "extremely regrettable", "dangerous" and "provocative", but also said that dialogue must remain an option.
China, for its part, has accused Japan of hyping the "China threat" in a bid to manipulate world public opinion against its giant neighbour.
"The Japanese side's remarks were against the facts," the defence ministry said in a statement.
"Japan unilaterally made public untrue information to the media and senior Japanese government officials made irresponsible remarks that hyped up the so-called 'China threat'," the ministry said.
A spokeswoman for China's foreign ministry said later that "Japan's remarks are completely making something out of nothing".