Japan yesterday said it could not guarantee that it would not 'take any action' against a Taiwanese plan to dispatch a warship to disputed waters around the Diaoyu Islands. The statement from a Japanese envoy in Taipei came ahead of today's scheduled 'inspection of Taiwanese waters' by Defence Minister Lee Jye. Along with legislative speaker Wang Jin-pyng and a dozen lawmakers, Mr Lee will board a Knox-class frigate and head to the waters near the archipelago claimed by Japan, Taiwan and the mainland. According to the government-funded Central News Agency, the Japanese envoy, Ikeda Tadashi, told the officials from the island's Foreign Ministry: 'The Japanese government does not think it is appropriate for the Ministry of Defence to dispatch a warship to protect [local] fishermen. 'It is inappropriate for military vessels to cross the mid-line of overlapping waters. The Japanese side cannot guarantee that it will not take any action if the Taiwanese warship does so.' Taiwan's Ministry of Defence has decided to back up the coastguard in its mission to patrol Taiwanese waters and protect local fishermen. The action is a result of strong protests by Taiwanese fishermen who have accused the government of inadequately protecting them while they are fishing in Taiwanese waters. The fishermen have threatened to seek help from the mainland and fly the Chinese flag if Taipei fails to do anything. The protests were sparked by frequent seizures of Taiwanese fishing boats by the Japanese coastguard, which has in the past two years beefed up patrols of Japan's 200 nautical mile economic zone that have reached even the northeastern part of Taiwan. Yesterday, Taipei Mayor Ma Ying-jeou demanded that the government take a tougher approach, even military action, to protect fishermen. 'I suggest that the government expand and give long-term protection for fishermen. If necessary, it should be willing to resort to military action in order to force [Japan] to compromise' with Taiwan, he said. Mr Wang yesterday also said it was necessary for the government to do all it could to protect the fishermen and Taiwan's 200-nautical-mile economic zone. He rejected accusations by ruling Democratic Progressive Party caucus head Lai Ching-teh that opposition politicians and legislators had tried to stage a political stunt by forcing the ministry to send a frigate to the disputed waters. 'It is highly improper for DPP legislators to look at the issue this way,' he said. Today's trip is expected to take about eight hours and finish in the afternoon. Mr Lai said Japan was friendly to Taiwan and opposition legislators who threatened to boycott Taipei's arms-purchase budget had confused the issue by treating Tokyo as an enemy. 'The biggest threat to Taiwan is from China,' Mr Lai said.