The US secretary of state has warned North Korea against following through on hints that it will carry out a missile launch.

"The possible missile launch that North Korea is talking about would be very unhelpful," Hillary Clinton said on Tuesday in Tokyo, the first stop on her maiden tour as Washington's chief diplomat.

Pyongyang had said on Monday, the 67th birthday of its leader Kim Jong-il, that it had the right to "space development", a term it has used in the past to describe a missile test.

Speaking to reporters in Tokyo, Clinton reiterated an offer to the North of a peace treaty as well as aid if it eliminated its nuclear weapons programme.

"If North Korea abides by the obligations it has already entered into and verifiably and completely eliminates its nuclear programme, then there will be a reciprocal response, certainly from the United States," she said.

"But the decision as to whether North Korea will co-operate in the six-party talks, end provocative language and actions, is up to them, and we are watching very closely."

Moving US troops

Clinton met her Japanese counterpart Hirofumi Nakasone on Tuesday and signed a deal to relocate 8,000 US marines from the Japanese island of Okinawa to the US Pacific island of Guam.

Okinawa residents have long complained about crime, pollution and crowding associated with the military base on their island, which holds about 20,000 US troops.

Anger against US troops on the island over a series of crimes in the past year has soured US-Japan ties.

The high-profile alleged rape of a 14-year-old Japanese girl by a US soldier and other reports of assaults triggered a curfew on troops by the military last year, limiting their movement on the Japanese island.

Balancing act

Clinton said "balance and harmony" would set the tone for the Obama administration's foreign policy, especially in tough economic times.

"We need to be looking to create more balance, more harmony."

"We're going to be listening but we're also going to be asking for more partnerships to come together to try to work with us to handle the problems that none of us can handle alone," she added, referring partly to the global financial crisis.

China's human rights and climate change are also expected to be on the agenda as she meets leaders on her Asia tour.

Clinton next visits Indonesia, followed by South Korea and China.