"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.
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.