Yasuo Fukuda appeared on Tuesday to be a shoo-in to become Japan's next prime minister but his rival, hawkish former foreign minister Taro Aso, vowed to battle on against all odds.

The 71-year-old former cabinet minister has emerged as the clear frontrunner in a party leadership race against Aso, 66, after conservative Prime Minister Shinzo Abe suddenly announced his resignation last week.

A survey by the Sankei newspaper showed that 60.3 percent of voters who support the ruling Liberal Democratic Party (LDP) favored Fukuda, double the 29.8 percent backing for Aso.

Earlier surveys have shown that Fukuda also has backing from a majority of the LDP lawmakers, who along with local party chapter representatives, will vote in the Sept 23 party poll.

The outspoken Aso, an early favorite who fell behind when the LDP's main factions agreed to support Fukuda, has been counting on support from LDP rank-and-file to turn the tide.

"The battle is from here on in," Aso told reporters after making the rounds of party lawmakers. "I will fight on to the end, for the sake of the LDP and for the sake of Japan."

Fukuda's fans see him as a moderate conservative who would bring political stability, while Aso is presenting himself as the bold leader Japan needs in a crisis.

"I support Fukuda. It seems like things could step back to where they were before, but he is more reliable," said Kyoko Usui, a 53-year-old calligrapher.

Fukuda would become the oldest Japanese premier since Kiichi Miyazawa took office in 1991 at the age of 72.

Ordinary Japanese voters have no direct say in the LDP poll of party chapters and lawmakers, to be held on September 23.

But their opinions matter, since the next prime minister is likely to have to lead his party into a general election that must be held by late 2009 but could well come sooner, given a potential standoff in parliament with opposition parties.

WARM-UP ACT?

"This is not the last act, it's just a warm-up," said Jesper Koll, president of investment advisory group Tantallon Research Japan. "It will most likely be an interim government, and nobody quite knows what will happen after that."

Sankei's polls showed that among the general public, Fukuda -- son of a former prime minister who favors warmer ties with Japan's Asian neighbors -- had 55.9 percent support, compared to 28.1 percent for Aso. That was in line with other surveys.

Whoever is elected president of the LDP is assured of the premiership, as the ruling coalition commands a firm majority in parliament's lower house, which picks the prime minister.

Abe, 52, abruptly announced his resignation last week after a year in office dogged by scandals and a huge July election defeat, saying he hoped to clear the path to extend a Japanese naval mission in support of U.S.-led operations in Afghanistan.

The main opposition Democratic Party and its small allies are against the mission to refuel coalition ships in the Indian Ocean, a step strongly sought by close ally Washington.

Both Fukuda and Aso have stressed the importance of extending the mission, but say they want to better explain why it is needed to the opposition and the public.

Public support for the mission appears to be growing.

The Sankei poll showed 48.7 percent of respondents favored extending the mission, compared to 39.1 percent who were against it. Earlier media surveys had shown more opposed than in favor.

Democratic Party leader Ichiro Ozawa, however, said he would not be swayed in his opposition to the Indian Ocean mission.

"Of course, we must always pay close heed to public opinion," he told a news conference. "But this (opposition to the mission) is something we have promised, and I think it will not change."

The opposition parties, which won control of parliament's upper house in the July election, can delay legislation to extend the mission beyond a November 1 deadline.

Fukuda said at the weekend it was theoretically possible for the ruling coalition to enact a law to extend the mission by overriding the upper house with its two-thirds majority in the lower chamber, but added doing so would be a last resort.

(Additional reporting by Yoko Kubota and George Nishiyama)

Japan