Japanese Chief Cabinet Secretary Shinzo Abe has formally announced his candidacy to succeed Prime Minister Junichiro Koizumi.
Shinzo Abe is known as an outspoken conservative
Mr Abe pledged a robust foreign policy and restated his aim of holding a referendum on constitutional revision.
Mr Abe, 51, is the clear front-runner to win the 20 September contest to become president of the ruling party.
The holder of this post is almost certain to be made prime minister when Mr Koizumi steps down on 30 September.
Mr Abe made his announcement at a news conference in Hiroshima.
"I have decided to run as a candidate to respond to and accept the warm and strong hopes of many Japanese people," he said.
Mr Abe is not expected to make major changes in policy if he becomes prime minister.
Like Mr Koizumi, he favours strengthening an alliance with the United States, and taking a tough stand against North Korea.
In fact he is seen as even more hawkish than the current prime minister on some foreign policy issues, raising fears that Japan's relations with China and South Korea - which have deteriorated markedly under Mr Koizumi - could worsen still further.
"Japan will follow a foreign policy that makes firm demands based on national interests," Mr Abe said in his speech.
He was keen to improve ties with China and South Korea, he said, but stressed that such a step required "efforts from each country".
He also spoke of the need to revise Japan's pacifist constitution, which bans the use of military force. "We need a new constitution that fits better for how Japan should be in the 21st century," he said.
Mr Abe did not comment on the issue of the Yasukuni shrine. He has backed Mr Koizumi's visits to the controversial shrine, which commemorates Japan's war dead, including convicted war criminals.
Japan's Asian neighbours always react angrily to such trips, saying the shrine glorifies Japan's past militarism.
Shinzo Abe is the son of Shintaro Abe, a former foreign minister, and the grandson of former Prime Minister Nobusuke Kishi, who was arrested as a suspected war criminal after World War II but never charged.
His rivals for the leadership are Finance Minister Sadakazu Tanigaki and Foreign Minister Taro Aso.
But as chief cabinet secretary, and Mr Koizumi's right-hand man, Mr Abe is the favourite for the top job.
As well as having the support of many key members of the ruling Liberal Democratic Party, he also enjoys a clear lead in opinion polls.