Tokyo must keep a thaw in ties with China on track, the frontrunner to be Japan's next prime minister said on Sunday, while urging Beijing to better explain its ballooning military spending.

Yasuo Fukuda, 71, an advocate of a less U.S.-centric foreign policy, is widely expected to beat hawkish former foreign minister Taro Aso in the Liberal Democratic Party (LDP) leadership race sparked by Shinzo Abe's abrupt decision last week to resign.

"The U.S.-Japan alliance is the cornerstone and we must place weight on that. But if there are deficiencies in other areas, we should fix them," Fukuda told public broadcaster NHK.

"Prime Minister Abe visited China and South Korea and relations improved. We must make that trend even firmer."

Fukuda also apologized for chaos created by Abe's move, which has raised fears of a policy vacuum in Japan.

"Our country is in an emergency situation, or rather, a crisis," he said in a speech at LDP party headquarters. "I feel that as a party member and as a member of the parliament, I must apologize."

Fukuda reiterated he would not visit Tokyo's Yasukuni Shrine, seen by many Asian countries as a symbol of Japan's past militarism, if he were chosen as the nation's new leader.

Sino-Japanese ties chilled under Abe's predecessor Junichiro Koizumi, largely because of the Japanese leader's visits to Yasukuni, but thawed after Abe's visit to Beijing last October.

Fukuda sounded a critical note towards Abe's proposal for a 'broader Asia' partnership of democracies that would include India, the United States and Australia -- but not China.

"China is making efforts toward a free economy, so if we say they must change their system completely, that would seem to be rejecting them," Fukuda told private broadcaster Asahi TV.

But he also urged China to make its bulging military spending more transparent.

"China has a responsibility to explain ... and obtain understanding," he said.

INDIAN OCEAN NAVAL MISSION

Fukuda, the son of a prime minister and known as a "shadow foreign minister" when he served in Koizumi's cabinet, looks on track to win the September 23 election for LDP president after gaining support of all the ruling party's biggest factions.

Whoever wins the LDP race is assured the premiership by virtue of the ruling coalition's huge majority in parliament's powerful lower house.

Abe had refused to quit after his ruling camp suffered a huge defeat in a July upper house poll, then shocked politicians and the public by announcing his resignation last week, saying he wanted to clear the way to resolve a standoff over Japan's naval mission in support of U.S.-led operations in Afghanistan.

The soft-spoken Fukuda stressed the importance of extending the Japanese naval mission to refuel coalition ships in the Indian Ocean, a step strongly urged by Washington but which Japan's opposition parties are against.

"Various countries including France, Germany and Pakistan have expressed appreciation of this activity ... and we want to continue it if we can, so we must explain this to the opposition parties," Fukuda told NHK, adding it was necessary to sell the mission to the Japanese public as well.

The main opposition Democratic Party and its allies won a majority in the July upper house election and can thus delay legislation to extend the naval mission.

Fukuda said 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 that doing so would be a measure of last resort.

Fukuda also sounded a softer note towards talks on normalizing ties with North Korea, long foiled by a feud over Japanese citizens kidnapped decades ago by Pyongyang.

"We must not close the road to talks," he told Fuji TV. "We must show that we are willing to have discussions."

Abe has insisted the feud over the abductees be resolved before Japan would give energy aid to North Korea as part of a six-way disarmament deal agreed earlier this year.

(Additional reporting by Yoko Kubota)

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