Prime Minister Shinzo Abe, a conservative who took office last month, backed a tough line on North Korea as he met with US Secretary of State Condoleezza Rice, who is on a four-nation tour in the wake of Pyongyang's nuclear test.
"Japan will make an effort to strengthen the Japan-US alliance, including on missile defence," Abe told Rice, according to Abe's adviser Hiroshige Seko, who also attended the meeting.
Rice in turn said that "strengthening and modernising the US-Japan alliance will be a base of responding to this situation" with North Korea, Seko said.
US State Department spokesman Sean McCormack said that Abe and Rice "talked about the importance of co-operative defence measures such as intelligence-sharing and missile defence."
More than any other country, Japan feels a direct threat from North Korea, which fired a missile over its main island in 1998.
The 1998 incident led the United States and Japan to team up to build a missile defence shield. The US military also installed Patriot surface-to-air missiles in Japan after North Korea test-fired seven missiles in July.
Abe, who rose to popularity by campaigning against North Korea, has championed a greater military role for Japan, which was forced by the United States to renounce the right to wage war after defeat in World War II.
US and Japanese officials said Abe and Rice agreed on the need to enforce sanctions on North Korea imposed last week by the UN Security Council.
"North Korea must understand that things will get worse if it fails to respond to the international community's concerns," Abe was quoted by Seko as telling Rice.
Rice had promised, after arriving Wednesday in Japan, that the United States was prepared to use the "full range" of its military to defend its allies.
North Korea's nuclear test last week has raised US fears of a nuclear arms race in East Asia and led to calls in Japan to debate the long-taboo idea of building its own atomic weapons.
Rice reaffirmed to Abe that "the United States regards Japan's security as US security," Seko said.
"She said that North Koreans should not believe they can change the security environment and that the Japan-US alliance has an ability to respond to their challenge," Seko said.
Abe has repeatedly ruled out acquiring nuclear weapons, but others in his ruling party, including Foreign Minister Taro Aso, have said the long-taboo option should at least be discussed.
Hiroshi Suzuki, the deputy cabinet secretary for public relations, played down the attention given to the calls to debate the nuclear option.
"Despite many reports inside and abroad suggesting that there could be a possible review, the Japanese government strictly upholds and adheres to its three non-nuclear principles" of not producing, possessing or allowing entry of nuclear weapons onto its territory, Suzuki said.
Rice was the first high-ranking US official to meet Abe since he took office last month, succeeding his mentor, Junichiro Koizumi, who was one of US President George W. Bush's closest foreign allies.
"Congratulations," Rice said to Abe in front of cameras as she entered his office.
Abe asked Rice to tell Bush that he is "looking forward to" holding their first summit on the sidelines of an Asia-Pacific summit in Vietnam in November.
In a meeting Wednesday with Aso, Rice praised Abe for visiting China and South Korea last week in a bid to improve ties that were tense under Koizumi, according to another Japanese official at the talks.

Copyright AFP (Agence France-Presse), 2006