TOKYO – The front-runner to become Japan’s next prime minister vowed today to extend his nation’s support for American-led operations in Afghanistan.

Ruling party veteran Yasuo Fukuda also said he would take a softer line with North Korea over its past abduction of Japanese nationals, a row that has threatened to upset negotiations over the communist country’s nuclear weapons.

The September 23 Liberal Democratic Party ballot to replace Prime Minister Abe, who abruptly resigned earlier this week, will pit the liberal Mr. Fukuda against the more hawkish former Foreign Minister Taro Aso.

Both candidates have said Japan cannot afford to drop out of the global war on terrorism and pledged to push to extend the country’s naval mission in the Indian Ocean.

“Our mission is highly regarded by the international community. We must win understanding for the need to extend,” Mr. Fukuda told a joint press conference today.

Since 2001, Japan’s navy has been providing fuel for American-led coalition forces in Afghanistan under an anti-terrorism law that has been extended three times.

But the country’s main opposition party, the Democratic Party of Japan, is against a further extension, saying coalition operations there have not been properly approved by the United Nations.

“We must not forget that Japanese nationals were also among victims of the terrorist attacks on the U.S.,” Mr. Aso said. “We have the responsibility to participate in the global war on terror.” Twenty-four Japanese citizens were killed in the September 11, 2001 attacks.

Mr. Abe had staked his job on pushing through a military extension. But he resigned on Wednesday, leaving the future of the mission in limbo and triggering political confusion in the world’s second-biggest economy.

The premier was later hospitalized for exhaustion and stress-related stomach problems.

Mr. Aso, 66, a high-profile member of the Abe administration, initially emerged as the front-runner to replace Mr. Abe. But support for Mr. Fukuda, 71, a critic of Mr. Abe, has jumped after several party heavyweights said they will back him.

Mr. Fukuda also led Mr. Aso in a public opinion poll conducted by Kyodo News agency released late yesterday.

Mr. Fukuda also said today he would stay away from a contentious war shrine if he becomes prime minister and seek better ties with Asian neighbors.

Tokyo’s Yasukuni shrine is vilified by critics because among the war dead honored are Japanese executed for wartime atrocities in Asia. Mr. Abe’s predecessor Junichiro Koizumi made repeated visits to the shrine, infuriating China and South Korea.

“There is no need to engage in actions resented by our neighbors. We must consider this issue very cautiously,” Mr. Fukuda said. He suggested that Japan set up a separate memorial to honor its war dead.

Mr. Fukuda said he would soften Tokyo’s stance toward North Korea over its abductions of Japanese in the 1970s and 80s. Pyongyang returned five abductees in 2002, claiming the rest were dead.

Mr. Abe had demanded proof no more Japanese were in North Korea, and refused to give aid to the country under a regional disarmament deal earlier this year.

“Recent talks have become deadlocked, as if there is no room for further negotiation,” Mr. Fukuda said. “We must work to let our opponents know that we are ready to negotiate.”

Mr. Aso indicated he would retain Mr. Abe’s hardline stance, saying Japan faced “the gravest threat from North Korea’s nukes and missiles” and that “without pressure, there can be no dialogue.”

The winner of the ballot, involving LDP lawmakers and regional party representatives, is assured election as prime minister by parliament because of the party’s majority in the powerful lower house.