Japan has issued a tourist visa to former Taiwanese President Lee Teng-hui, despite protests from China.
China views Mr Lee as an agitator for Taiwan independence
Tokyo insists Mr Lee is visiting as a private citizen and therefore his trip does not violate Japan's ban on official contacts with Taiwan.
But China warned last week that bilateral relations would be harmed if Japan granted the visa.
The visa row coincides with a period of tension between China and Japan, who often compete for regional resources.
Mr Lee's visa will allow him to enter Japan once and stay up to 15 days.
Japanese Prime Minister Junichiro Koizumi told reporters that Mr Lee was travelling to Japan as a tourist, not a politician, "so there
is no reason to turn down his application".
It has been four years since Mr Lee left office, but Beijing makes a point of objecting to other countries giving him access.
In Chinese eyes, even the smallest concessions on this issue could shore up Taiwanese dreams of independence, according to the BBC correspondent in Tokyo, Jonathan Head.
During his 12 years as Taiwanese president, Mr Lee edged the island towards formal independence, infuriating Beijing, which sees Taiwan as a breakaway province.
The last time Mr Lee visited Japan was in 2001 for medical treatment. That trip also sparked Chinese anger.
Relations between China and Japan have been soured in recent weeks by an alleged incursion by a Chinese submarine into Japanese waters, and a continuing row over repeated visits by Mr Koizumi to the country's Yasukuni Shrine.
The shrine is dedicated to the souls of the country's war dead, including convicted war criminals, and is viewed by other Asian nations as a symbol of Japanese wartime aggression.