TOKYO - A plan by Japan's center-left leaders to give foreigners the vote in local elections has sparked a conservative backlash, showing ethnic minority issues can touch a raw nerve in the island-nation.

The idea is to grant local and regional but not national suffrage to almost one million permanent residents of ethnic Korean, Chinese and other foreign backgrounds, both those who were born overseas and their descendants.

But when the Democratic Party of Japan (DPJ) under Prime Minister Yukio Hatoyama floated the idea for the current parliamentary session, a key coalition partner quickly managed to derail the plan, at least temporarily.

Siding with protests from the conservative opposition, the maverick leader of the tiny People's New Party, Financial Services Minister Shizuka Kamei, this month threatened to quit the government over the issue.

"The coalition will collapse" said Kamei, warning that letting foreigners vote would "stir ethnic sentiments and risk generating confrontation."

Kamei's move looks likely to put the plan on ice at least until after July upper house elections, the latest hurdle in a debate over voting rights for foreigners that also include minorities from Brazil, Peru and the Philippines.

Japan has long kept a tight lid on immigration, making the country of 128 million one of the world's most ethnically homogeneous major democracies.

Nationality in Japan is based on parentage rather than birthplace, meaning that even third-generation "foreigners" who pay taxes do not get to vote, unless they adopt Japanese nationality. Dual nationality is not allowed.

When Hatoyama's DPJ swept to power in August elections, ending a half-century of conservative rule, the local suffrage plan for 910,000 permanent foreign residents was part of its sweeping reformist agenda.

Despite fierce opposition from conservatives, 59 percent of Japanese voters support giving local suffrage to foreigners, against 31 percent who oppose it, according to a November poll by the Mainichi Shimbun daily.

The idea promised "what we have long craved, because we have fought against racial discrimination for decades," said Kim Jong-Soo, 33, former president of the Korean Youth Association in Japan.

Ethnic Koreans until recently made up the largest foreign community in Japan, most of them descendants of migrants and forced laborers taken to Japan when it ruled the Korean peninsula between 1910 and 1945.

"My parents' generation suffered discrimination in employment, marriage and in being able to rent houses," Kim said. "Today most of this is obsolete, but local suffrage is the final step to ending the discrimination."

People of Chinese descent -- the biggest foreign community since 2007 as economic links between the Asian giants have grown -- also welcomed the move.

Voting rights for the foreigners "would nudge assembly members to listen to ethnic minorities' everyday concerns," said Duan Yuezhong, 51, who came to Japan in 1991 and obtained Japanese nationality three years ago.

Critics of the DPJ plan have touched on deeper fears about threats to Japan's national sovereignty, especially in hot-button territorial disputes over islands also claimed by Japan's neighbors.

If given voting rights, ethnic Koreans would have more of a platform to push for Takeshima island, called Dokdo by Koreans, to come under Seoul's sovereignty, they argue.

The assembly speaker of the western prefecture of Shimane told AFP that "our people are worried that giving voting rights to foreigners will have a grave impact on the territorial issue of Takeshima."

The same applies with rows over the Senkaku islands, known as the Diaoyu islands in Chinese, which are also claimed by Beijing and Taipei.

Duan dismissed those ideas as "delusional thinking" and said Japan should look to other countries, where people of different ethnic backgrounds have become trusted citizens and even government leaders.

"I believe it's good for both Japan and China that Chinese-Japanese are active in politics," he said. "Ethnic Chinese, who are familiar with China's sociopolitical issues, can help improve Japan's relations with China."