Activists and observers across the Taiwan Straits have called on the island to cooperate with the Chinese mainland in safeguarding the sovereignty of the Diaoyu Islands in the East China Sea, after Japan Tuesday responded to a peace initiative proposed by Taiwan leader Ma Ying-jeou.

During a press conference on Tuesday, Japan's Foreign Minister Koichiro Gemba said "Japan does not accept Taiwan's claim of sovereignty" over the Diaoyu Islands, but considered Ma's proposal an option for concerned parties to cooperate in various ways to maintain peace and stability in the region, the Taipei Times reported.

Ma proposed the East China Sea Peace Initiative aimed at settling the Diaoyu Islands disputes and promoting cooperation, including joint exploration and development in the area.

Ma expressed his concerns regarding recent moves taken by Japan on the Diaoyu Islands.

In the initiative, he called on all concerned parties to refrain from taking any antagonistic actions, and seek consensus on a code of conduct in the East China Sea.

Huang Hsi-lin, chairman of a Taiwan-based activist group defending the Diaoyu Islands, blamed Ma for taking an equivocal stance on the disputes, and insisted that his peace initiative could not solve them.

"Only through the cooperation of Taiwan and the Chinese mainland can the disputes over the Diaoyu Islands be solved," he told the Global Times.

Huang's comments were echoed by Li Jiaquan, a researcher with the Chinese Academy of Social Sciences, who contended Ma should draw a lesson from Japan's response to the peace initiative.

Li also said that Ma's proposal came at a time when he was accused by many Taiwan people of being too weak on the issue.